# What is CVE-2021-34991? > CVE-2021-34991 is a high-severity flaw (CVSS 8.8) in R6400 from Netgear, published on 15 November 2021. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 5.7%. If you run an affected version, plan in the vendor’s fix. Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-34991 ## At a glance - **Verdict:** Plan it in. No sign of exploitation and a low forecast. Patch it in your normal update cycle. - **Precursor Intelligence risk score:** 49 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes. - **Severity:** High (CVSS 8.8 out of 10) - **Known to be exploited:** No, not on the list of flaws known to be exploited today - **Chance of use in the next 30 days:** 5.7% (latest exploit-likelihood forecast) - **Published:** 15 November 2021 - **Record last updated:** 17 November 2021 - **Main product:** R6400 from Netgear - **Affected products:** 88 ## What is CVE-2021-34991? In plain terms An attacker has to be on the same local network without logging in, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline. ### The official description This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400v2 1.0.4.106_10.0.80 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the UPnP service, which listens on TCP port 5000 by default. When parsing the uuid request header, the process does not properly validate the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-14110. ### What kind of flaw is it? - CWE-787: Out-of-bounds Write - CWE-121: Stack-based Buffer Overflow ### How an attack on it works - Where an attacker can be: On the same local network - How hard it is to pull off: Easy: no special conditions - Login needed first: No login needed - Does someone have to click: No, nobody has to do anything - What an attacker gets: Can read data, change data and take it offline Severity vector: `CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H` ## Is CVE-2021-34991 being exploited? Not that we know of It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 5.7%. That can change at any time, which is why we keep watching. Exploit likelihood over the last 7 days: 5.7%, 5.7%, 5.7%, 5.7%, 5.7%, 5.7%, 5.7%. ### Timeline - 15 November 2021: Published - 17 November 2021: Record last updated ### How Precursor Intelligence ranks it CVE-2021-34991 scores **49 out of 100 (Medium)**, with the action "Plan remediation". Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less: - Evidence it is being exploited: biggest factor - How severe it is: strong factor - How widely exposed it is: key context - Real threat activity around it: key context 85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it. ## Who is affected by CVE-2021-34991? The published record lists 88 products. Versions are as published: "before 2.1.3.5" means every version up to, but not including, 2.1.3.5. - [R6400](https://www.precursorintelligence.com/product/netgear/r6400) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Cax80](https://www.precursorintelligence.com/product/netgear/cax80) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Cax80 Firmware](https://www.precursorintelligence.com/product/netgear/cax80_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 2.1.3.5 - [D6220](https://www.precursorintelligence.com/product/netgear/d6220) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [D6220 Firmware](https://www.precursorintelligence.com/product/netgear/d6220_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.76 - [D6400](https://www.precursorintelligence.com/product/netgear/d6400) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [D6400 Firmware](https://www.precursorintelligence.com/product/netgear/d6400_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.108 - [D7000v2](https://www.precursorintelligence.com/product/netgear/d7000v2) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [D7000v2 Firmware](https://www.precursorintelligence.com/product/netgear/d7000v2_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.76 - [Dc112a](https://www.precursorintelligence.com/product/netgear/dc112a) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Dc112a Firmware](https://www.precursorintelligence.com/product/netgear/dc112a_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.62 - [Dgn2200v4](https://www.precursorintelligence.com/product/netgear/dgn2200v4) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Dgn2200v4 Firmware](https://www.precursorintelligence.com/product/netgear/dgn2200v4_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.126 - [Ex3700](https://www.precursorintelligence.com/product/netgear/ex3700) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Ex3700 Firmware](https://www.precursorintelligence.com/product/netgear/ex3700_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.94 - [Ex3800](https://www.precursorintelligence.com/product/netgear/ex3800) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Ex3800 Firmware](https://www.precursorintelligence.com/product/netgear/ex3800_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.94 - [Ex6120](https://www.precursorintelligence.com/product/netgear/ex6120) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Ex6120 Firmware](https://www.precursorintelligence.com/product/netgear/ex6120_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.66 - [Ex6130](https://www.precursorintelligence.com/product/netgear/ex6130) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Ex6130 Firmware](https://www.precursorintelligence.com/product/netgear/ex6130_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.66 - [R6400 Firmware](https://www.precursorintelligence.com/product/netgear/r6400_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.1.76 - [R6400v2](https://www.precursorintelligence.com/product/netgear/r6400v2) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R6400v2 Firmware](https://www.precursorintelligence.com/product/netgear/r6400v2_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.120 - [R6700v3](https://www.precursorintelligence.com/product/netgear/r6700v3) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R6700v3 Firmware](https://www.precursorintelligence.com/product/netgear/r6700v3_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.120 - [R6900p](https://www.precursorintelligence.com/product/netgear/r6900p) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R6900p Firmware](https://www.precursorintelligence.com/product/netgear/r6900p_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.3.3.142 - [R7000](https://www.precursorintelligence.com/product/netgear/r7000) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R7000 Firmware](https://www.precursorintelligence.com/product/netgear/r7000_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.11.128 - [R7000p](https://www.precursorintelligence.com/product/netgear/r7000p) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R7000p Firmware](https://www.precursorintelligence.com/product/netgear/r7000p_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.3.3.142 - [R7100lg](https://www.precursorintelligence.com/product/netgear/r7100lg) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R7100lg Firmware](https://www.precursorintelligence.com/product/netgear/r7100lg_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.0.72 - [R7850](https://www.precursorintelligence.com/product/netgear/r7850) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R7850 Firmware](https://www.precursorintelligence.com/product/netgear/r7850_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.5.76 - [R7900p](https://www.precursorintelligence.com/product/netgear/r7900p) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R7900p Firmware](https://www.precursorintelligence.com/product/netgear/r7900p_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.4.2.84 - [R7960p](https://www.precursorintelligence.com/product/netgear/r7960p) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R7960p Firmware](https://www.precursorintelligence.com/product/netgear/r7960p_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.4.2.84 - [R8000](https://www.precursorintelligence.com/product/netgear/r8000) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R8000 Firmware](https://www.precursorintelligence.com/product/netgear/r8000_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.76 - [R8000p](https://www.precursorintelligence.com/product/netgear/r8000p) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R8000p Firmware](https://www.precursorintelligence.com/product/netgear/r8000p_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.4.2.84 - [R8300](https://www.precursorintelligence.com/product/netgear/r8300) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R8300 Firmware](https://www.precursorintelligence.com/product/netgear/r8300_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.2.156 - [R8500](https://www.precursorintelligence.com/product/netgear/r8500) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R8500 Firmware](https://www.precursorintelligence.com/product/netgear/r8500_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.2.156 - [Rax15](https://www.precursorintelligence.com/product/netgear/rax15) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax15 Firmware](https://www.precursorintelligence.com/product/netgear/rax15_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax20](https://www.precursorintelligence.com/product/netgear/rax20) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax20 Firmware](https://www.precursorintelligence.com/product/netgear/rax20_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax200](https://www.precursorintelligence.com/product/netgear/rax200) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax200 Firmware](https://www.precursorintelligence.com/product/netgear/rax200_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.5.132 - [Rax35v2](https://www.precursorintelligence.com/product/netgear/rax35v2) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax35v2 Firmware](https://www.precursorintelligence.com/product/netgear/rax35v2_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax38v2](https://www.precursorintelligence.com/product/netgear/rax38v2) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax38v2 Firmware](https://www.precursorintelligence.com/product/netgear/rax38v2_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax40v2](https://www.precursorintelligence.com/product/netgear/rax40v2) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax40v2 Firmware](https://www.precursorintelligence.com/product/netgear/rax40v2_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax42](https://www.precursorintelligence.com/product/netgear/rax42) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax42 Firmware](https://www.precursorintelligence.com/product/netgear/rax42_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax43](https://www.precursorintelligence.com/product/netgear/rax43) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax43 Firmware](https://www.precursorintelligence.com/product/netgear/rax43_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax45](https://www.precursorintelligence.com/product/netgear/rax45) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax45 Firmware](https://www.precursorintelligence.com/product/netgear/rax45_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax48](https://www.precursorintelligence.com/product/netgear/rax48) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax48 Firmware](https://www.precursorintelligence.com/product/netgear/rax48_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax50](https://www.precursorintelligence.com/product/netgear/rax50) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax50 Firmware](https://www.precursorintelligence.com/product/netgear/rax50_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax50s](https://www.precursorintelligence.com/product/netgear/rax50s) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax50s Firmware](https://www.precursorintelligence.com/product/netgear/rax50s_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.4.100 - [Rax75](https://www.precursorintelligence.com/product/netgear/rax75) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax75 Firmware](https://www.precursorintelligence.com/product/netgear/rax75_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.5.132 - [Rax80](https://www.precursorintelligence.com/product/netgear/rax80) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rax80 Firmware](https://www.precursorintelligence.com/product/netgear/rax80_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.5.132 - [Raxe450](https://www.precursorintelligence.com/product/netgear/raxe450) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Raxe450 Firmware](https://www.precursorintelligence.com/product/netgear/raxe450_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.8.70 - [Raxe500](https://www.precursorintelligence.com/product/netgear/raxe500) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Raxe500 Firmware](https://www.precursorintelligence.com/product/netgear/raxe500_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.8.70 - [Rs400](https://www.precursorintelligence.com/product/netgear/rs400) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Rs400 Firmware](https://www.precursorintelligence.com/product/netgear/rs400_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.5.1.80 - [Wndr3400v3](https://www.precursorintelligence.com/product/netgear/wndr3400v3) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Wndr3400v3 Firmware](https://www.precursorintelligence.com/product/netgear/wndr3400v3_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.1.42 - [Wnr3500lv2](https://www.precursorintelligence.com/product/netgear/wnr3500lv2) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Wnr3500lv2 Firmware](https://www.precursorintelligence.com/product/netgear/wnr3500lv2_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.2.0.70 - [Xr300](https://www.precursorintelligence.com/product/netgear/xr300) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [Xr300 Firmware](https://www.precursorintelligence.com/product/netgear/xr300_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): before 1.0.3.68 ## How do I fix CVE-2021-34991? 1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list. 2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisory first in the list. 3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in. 4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood. ### References - [kb.netgear.com](https://kb.netgear.com/000064361/Security-Advisory-for-Pre-Authentication-Buffer-Overflow-on-Multiple-Products-PSV-2021-0168) (Vendor advisory) - [zerodayinitiative.com](https://www.zerodayinitiative.com/advisories/ZDI-21-1303/) (Third-party advisory, Vulnerability database) ## Questions ### What is CVE-2021-34991? CVE-2021-34991 is a high-severity flaw in R6400 from Netgear, published on 15 November 2021. An attacker has to be on the same local network without logging in, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline. ### How serious is CVE-2021-34991? It scores 8.8 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2021-34991 is 49 out of 100, which is Medium. Its action is "Plan remediation". No sign of exploitation and a low forecast. Patch it in your normal update cycle. ### Is CVE-2021-34991 being exploited? It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 5.7%. That can change at any time, which is why we keep watching. ### Which versions does CVE-2021-34991 affect? For R6400 from Netgear: version not specified. The record lists 88 products in all, each with its versions, under "Who is affected" on this page. ### How do I fix CVE-2021-34991? Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet. ## Does CVE-2021-34991 affect you? Precursor Intelligence keeps checking for you: - **Tell us what you run.** Pick your software from a list, or let us work it out from your website. - **We match it to every flaw.** Over 400,000 published flaws, checked against your list. - **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it. - **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools. Start free (no card, nothing to install): https://www.precursorintelligence.com/register Book a demo: https://www.precursorintelligence.com/contact