CVE-2025-21846

CVE-2025-21846 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

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.

Frequently asked questions

What is CVE-2025-21846?
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.
How severe is CVE-2025-21846?
CVE-2025-21846 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-21846 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21846?
CVE-2025-21846 primarily affects Linux Linux Kernel. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-21846?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-21846 have an EU (EUVD) identifier?
Yes. CVE-2025-21846 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-6290.
When was CVE-2025-21846 published?
CVE-2025-21846 was published on 2025-03-12 and last updated on 2026-06-17.

References

Affected products (4)

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