# What is CVE-2021-40847? > CVE-2021-40847 is a high-severity flaw (CVSS 8.1) in R6400v2 from Netgear, published on 21 September 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 10%. If you run an affected version, plan in the vendor’s fix. Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-40847 ## At a glance - **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month. - **Precursor Intelligence risk score:** 54 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes. - **Severity:** High (CVSS 8.1 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:** 10% (latest exploit-likelihood forecast) - **Published:** 21 September 2021 - **Record last updated:** 7 October 2021 - **Main product:** R6400v2 from Netgear - **Affected products:** 22 ## What is CVE-2021-40847? In plain terms It can be attacked from anywhere on the internet 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 The update process of the Circle Parental Control Service on various NETGEAR routers allows remote attackers to achieve remote code execution as root via a MitM attack. While the parental controls themselves are not enabled by default on the routers, the Circle update daemon, circled, is enabled by default. This daemon connects to Circle and NETGEAR to obtain version information and updates to the circled daemon and its filtering database. However, database updates from NETGEAR are unsigned and downloaded via cleartext HTTP. As such, an attacker with the ability to perform a MitM attack on the device can respond to circled update requests with a crafted, compressed database file, the extraction of which gives the attacker the ability to overwrite executable files with attacker-controlled code. This affects R6400v2 1.0.4.106, R6700 1.0.2.16, R6700v3 1.0.4.106, R6900 1.0.2.16, R6900P 1.3.2.134, R7000 1.0.11.123, R7000P 1.3.2.134, R7850 1.0.5.68, R7900 1.0.4.38, R8000 1.0.4.68, and RS400 1.5.0.68. ### What kind of flaw is it? - CWE-319: Cleartext Transmission of Sensitive Information ### How an attack on it works - Where an attacker can be: Anywhere on the internet - How hard it is to pull off: Hard: conditions must line up - 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:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H` ## Is CVE-2021-40847 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 10%. That can change at any time, which is why we keep watching. Exploit likelihood over the last 7 days: 10%, 10%, 10%, 10%, 10%, 10%, 10%. ### Timeline - 21 September 2021: Published - 7 October 2021: Record last updated ### How Precursor Intelligence ranks it CVE-2021-40847 scores **54 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-2021-40847? The published record lists 22 products. - [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): 1.0.4.106 - [R6700](https://www.precursorintelligence.com/product/netgear/r6700) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R6700 Firmware](https://www.precursorintelligence.com/product/netgear/r6700_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): 1.0.2.16 - [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): 1.0.4.106 - [R6900](https://www.precursorintelligence.com/product/netgear/r6900) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R6900 Firmware](https://www.precursorintelligence.com/product/netgear/r6900_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): 1.0.2.16 - [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): 1.3.2.134 - [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): 1.0.11.123 - [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): 1.3.2.134 - [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): 1.0.5.68 - [R7900](https://www.precursorintelligence.com/product/netgear/r7900) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Hardware): version not specified - [R7900 Firmware](https://www.precursorintelligence.com/product/netgear/r7900_firmware) by [Netgear](https://www.precursorintelligence.com/vendors/netgear) (Operating system): 1.0.4.38 - [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): 1.0.4.68 - [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): 1.5.0.68 ## How do I fix CVE-2021-40847? 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/000064039/Security-Advisory-for-Remote-Code-Execution-on-Some-Routers-PSV-2021-0204) (Vendor advisory) - [blog.grimm-co.com](https://blog.grimm-co.com/2021/09/mama-always-told-me-not-to-trust.html) (Exploit, Third-party advisory) ## Questions ### What is CVE-2021-40847? CVE-2021-40847 is a high-severity flaw in R6400v2 from Netgear, published on 21 September 2021. It can be attacked from anywhere on the internet 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-2021-40847? It scores 8.1 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2021-40847 is 54 out of 100, which is Medium. Its action is "Plan remediation". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month. ### Is CVE-2021-40847 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 10%. That can change at any time, which is why we keep watching. ### Which versions does CVE-2021-40847 affect? For R6400v2 from Netgear: version not specified. The record lists 22 products in all, each with its versions, under "Who is affected" on this page. ### How do I fix CVE-2021-40847? 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-2021-40847 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