# What is CVE-2020-3524? > CVE-2020-3524 is a medium-severity flaw (CVSS 6.8) in Ios XE Rom Monitor from Cisco, published on 24 September 2020. 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 0.3%. If you run an affected version, plan in the vendor’s fix. Canonical page: https://www.precursorintelligence.com/what-is/cve-2020-3524 ## 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:** 21 out of 100 (Low); action: Monitor. Kept up to date as the evidence changes. - **Severity:** Medium (CVSS 6.8 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:** 0.3% (latest exploit-likelihood forecast) - **Published:** 24 September 2020 - **Record last updated:** 22 May 2023 - **Main product:** Ios XE Rom Monitor from Cisco - **Affected products:** 26 ## What is CVE-2020-3524? In plain terms An attacker has to be physically at the device 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 A vulnerability in the Cisco IOS XE ROM Monitor (ROMMON) Software for Cisco 4000 Series Integrated Services Routers, Cisco ASR 920 Series Aggregation Services Routers, Cisco ASR 1000 Series Aggregation Services Routers, and Cisco cBR-8 Converged Broadband Routers could allow an unauthenticated, physical attacker to break the chain of trust and load a compromised software image on an affected device. The vulnerability is due to the presence of a debugging configuration option in the affected software. An attacker could exploit this vulnerability by connecting to an affected device through the console, forcing the device into ROMMON mode, and writing a malicious pattern using that specific option on the device. A successful exploit could allow the attacker to break the chain of trust and load a compromised software image on the affected device. A compromised software image is any software image that has not been digitally signed by Cisco. ### What kind of flaw is it? - CWE-862: Missing Authorization - CWE-284: Improper Access Control ### How an attack on it works - Where an attacker can be: Physically at the device - 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:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H` ## Is CVE-2020-3524 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 0.3%. That can change at any time, which is why we keep watching. Exploit likelihood over the last 7 days: 0.3%, 0.3%, 0.3%, 0.3%, 0.3%, 0.3%, 0.3%. ### Timeline - 24 September 2020: Published - 22 May 2023: Record last updated ### How Precursor Intelligence ranks it CVE-2020-3524 scores **21 out of 100 (Low)**, with the action "Monitor". 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-2020-3524? The published record lists 26 products. Versions are as published: "before 16.2(1r)" means every version up to, but not including, 16.2(1r). - [Ios XE Rom Monitor](https://www.precursorintelligence.com/product/cisco/ios_xe_rom_monitor) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Operating system): before 16.2(1r), before 15.6(18r), before 16.4(1r)s - [4221 Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4221_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [4331 Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4331_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [4431 Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4431_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [4461 Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4461_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR 1000-X](https://www.precursorintelligence.com/product/cisco/asr_1000-x) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR 1001](https://www.precursorintelligence.com/product/cisco/asr_1001) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR 1001-X](https://www.precursorintelligence.com/product/cisco/asr_1001-x) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR 1002](https://www.precursorintelligence.com/product/cisco/asr_1002) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR 1002-X](https://www.precursorintelligence.com/product/cisco/asr_1002-x) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR 1004](https://www.precursorintelligence.com/product/cisco/asr_1004) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR 1006](https://www.precursorintelligence.com/product/cisco/asr_1006) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR 1013](https://www.precursorintelligence.com/product/cisco/asr_1013) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR 920u-12sz-Im](https://www.precursorintelligence.com/product/cisco/asr_920u-12sz-im) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-10sz-Pd](https://www.precursorintelligence.com/product/cisco/asr-920-10sz-pd) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-12cz-a](https://www.precursorintelligence.com/product/cisco/asr-920-12cz-a) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-12cz-D](https://www.precursorintelligence.com/product/cisco/asr-920-12cz-d) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-12sz-a](https://www.precursorintelligence.com/product/cisco/asr-920-12sz-a) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-12sz-D](https://www.precursorintelligence.com/product/cisco/asr-920-12sz-d) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-20sz-M](https://www.precursorintelligence.com/product/cisco/asr-920-20sz-m) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-24sz-Im](https://www.precursorintelligence.com/product/cisco/asr-920-24sz-im) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-24sz-M](https://www.precursorintelligence.com/product/cisco/asr-920-24sz-m) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-24tz-M](https://www.precursorintelligence.com/product/cisco/asr-920-24tz-m) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-4sz-a](https://www.precursorintelligence.com/product/cisco/asr-920-4sz-a) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [ASR-920-4sz-D](https://www.precursorintelligence.com/product/cisco/asr-920-4sz-d) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified - [Cbr8](https://www.precursorintelligence.com/product/cisco/cbr8) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified ## How do I fix CVE-2020-3524? 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 - [tools.cisco.com](https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-rommon-secboot-7JgVLVYC) (Vendor advisory) ## Questions ### What is CVE-2020-3524? CVE-2020-3524 is a medium-severity flaw in Ios XE Rom Monitor from Cisco, published on 24 September 2020. An attacker has to be physically at the device 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-2020-3524? It scores 6.8 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2020-3524 is 21 out of 100, which is Low. Its action is "Monitor". No sign of exploitation and a low forecast. Patch it in your normal update cycle. ### Is CVE-2020-3524 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 0.3%. That can change at any time, which is why we keep watching. ### Which versions does CVE-2020-3524 affect? For Ios XE Rom Monitor from Cisco: before 16.2(1r), before 15.6(18r), before 16.4(1r)s. The record lists 26 products in all, each with its versions, under "Who is affected" on this page. ### How do I fix CVE-2020-3524? 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-2020-3524 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