# What is CVE-2021-26932? > CVE-2021-26932 is a medium-severity flaw (CVSS 5.5) in Linux kernel, published on 17 February 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 0.3%. If you run an affected version, plan in the vendor’s fix. Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-26932 ## 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:** 17 out of 100 (Info); action: Track. Kept up to date as the evidence changes. - **Severity:** Medium (CVSS 5.5 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:** 17 February 2021 - **Record last updated:** 25 March 2024 - **Main product:** Linux kernel - **Affected products:** 9 ## What is CVE-2021-26932? In plain terms An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can take it offline. ### The official description An issue was discovered in the Linux kernel 3.2 through 5.10.16, as used by Xen. Grant mapping operations often occur in batch hypercalls, where a number of operations are done in a single hypercall, the success or failure of each one is reported to the backend driver, and the backend driver then loops over the results, performing follow-up actions based on the success or failure of each operation. Unfortunately, when running in PV mode, the Linux backend drivers mishandle this: Some errors are ignored, effectively implying their success from the success of related batch elements. In other cases, errors resulting from one batch element lead to further batch elements not being inspected, and hence successful ones to not be possible to properly unmap upon error recovery. Only systems with Linux backends running in PV mode are vulnerable. Linux backends run in HVM / PVH modes are not vulnerable. This affects arch/*/xen/p2m.c and drivers/xen/gntdev.c. ### What kind of flaw is it? - Unknown: Unknown ### How an attack on it works - Where an attacker can be: Already on the device - How hard it is to pull off: Easy: no special conditions - Login needed first: An ordinary user account - Does someone have to click: No, nobody has to do anything - What an attacker gets: Can take it offline Severity vector: `CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` ## Is CVE-2021-26932 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 - 17 February 2021: Published - 25 March 2024: Record last updated ### How Precursor Intelligence ranks it CVE-2021-26932 scores **17 out of 100 (Info)**, with the action "Track". 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: smaller factor - Threat activity around it: smaller factor 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-2021-26932? The published record lists 9 products. - [Linux kernel](https://www.precursorintelligence.com/product/linux/linux_kernel) by [Linux](https://www.precursorintelligence.com/vendors/linux) (Operating system): 3.2 to 5.10.16 - [Fedora](https://www.precursorintelligence.com/product/fedoraproject/fedora) by [Fedoraproject](https://www.precursorintelligence.com/vendors/fedoraproject) (Operating system): 32, 33 - [Cloud Backup](https://www.precursorintelligence.com/product/netapp/cloud_backup) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified - [Debian Linux](https://www.precursorintelligence.com/product/debian/debian_linux) by [Debian](https://www.precursorintelligence.com/vendors/debian) (Operating system): 9.0 - [Hci Compute Node](https://www.precursorintelligence.com/product/netapp/hci_compute_node) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified - [Hci H410c](https://www.precursorintelligence.com/product/netapp/hci_h410c) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified - [Hci H410c Firmware](https://www.precursorintelligence.com/product/netapp/hci_h410c_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified - Solidfire & Hci Management Node by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified - Solidfire, Enterprise Sds & Hci Storage Node by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified ## How do I fix CVE-2021-26932? 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 - [xenbits.xen.org](http://xenbits.xen.org/xsa/advisory-361.html) (Patch, Third-party advisory) - [git.kernel.org](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ebee0eab08594b2bd5db716288a4f1ae5936e9bc) - [lists.debian.org](https://lists.debian.org/debian-lts-announce/2021/03/msg00010.html) (Mailing list, Third-party advisory) - [lists.debian.org](https://lists.debian.org/debian-lts-announce/2021/03/msg00035.html) (Mailing list, Third-party advisory) - [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2XQR52ICKRK3GC4HDWLMWF2U55YGAR63/) - [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GWQWPWYZRXVFJI5M3VCM72X27IB7CKOB/) - [security.netapp.com](https://security.netapp.com/advisory/ntap-20210326-0001/) (Third-party advisory) ## Questions ### What is CVE-2021-26932? CVE-2021-26932 is a medium-severity flaw in Linux kernel, published on 17 February 2021. An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can take it offline. ### How serious is CVE-2021-26932? It scores 5.5 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2021-26932 is 17 out of 100, which is Info. Its action is "Track". No sign of exploitation and a low forecast. Patch it in your normal update cycle. ### Is CVE-2021-26932 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-2021-26932 affect? For Linux kernel: 3.2 to 5.10.16. The record lists 9 products in all, each with its versions, under "Who is affected" on this page. ### How do I fix CVE-2021-26932? 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-2021-26932 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