Linux Kernel: memory corruption flaw under attack

What is affected

Linux Kernel is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.

Linux Kernel contains a race condition vulnerability which allows concurrent writes to the same AF_ALG socket causing data to be unpredictably interleaved and creating inconsistencies in the socket's internal state.

What an attacker can do

This is a memory corruption flaw. It lets an attacker corrupt the program's memory by feeding it specially crafted content: a web page, a file or a network message. The result ranges from a crash to the attacker running their own code.

How it is reached

Needs access to the device or a file opened on it

Access the attacker needs

A basic user account

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. Update Linux Kernel now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
2. Turn on automatic updates so the next fix arrives without you having to look for it.
3. If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Vendor advisories and fixes

• git.kernel.orggit.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce
• git.kernel.orggit.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9
• git.kernel.orggit.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8
• git.kernel.orggit.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84
• git.kernel.orggit.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d
• git.kernel.orggit.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on September 18, 2026, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by September 21, 2026, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 1.3% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 69% of all scored vulnerabilities.

Its CVSS severity score is 5.5 out of 10 (medium), as recorded in the US National Vulnerability Database.

Technical description

In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg Issuing two writes to the same af_alg socket is bogus as the data will be interleaved in an unpredictable fashion. Furthermore, concurrent writes may create inconsistencies in the internal socket state. Disallow this by adding a new ctx->write field that indiciates exclusive ownership for writing.