CVE-2025-21846 acct: perform last write from workqueue

What is CVE-2025-21846?

CVE-2025-21846 is a medium-severity vulnerability in Linux kernel, published on 12 Mar 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

acct: perform last write from workqueue

In [1] it was reported that the acct(2) system call can be used to trigger NULL deref in cases where it is set to write to a file that triggers an internal lookup. This can e.g., happen when pointing acc(2) to /sys/power/resume. At the point the where the write to this file happens the calling task has already exited and called exit_fs(). A lookup will thus trigger a NULL-deref when accessing current->fs.

Reorganize the code so that the the final write happens from the workqueue but with the caller's credentials. This preserves the (strange) permission model and has almost no regression risk.

This api should stop to exist though.

Weakness: CWE-476

Which versions are affected by CVE-2025-21846?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21846?

Apply the vendor's patch.

Is CVE-2025-21846 being exploited?

There is no known exploitation of CVE-2025-21846 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-58532, AZL-58569, BELL-CVE-2025-21846, DEBIAN-CVE-2025-21846, GHSA-wg7v-626p-h26r, ROOT-OS-UBUNTU-2404-CVE-2025-21846 and 1 more.