CVE-2026-74321: Linux Vulnerability (CVSS 7.5)

Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs() In the beginning of the loop, we try to obtain a locked delayed ref head, if 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(), which can return an error pointer. If the error pointer is -EAGAIN we do a continue and go back to the beginning of the loop, which will not try again to call btrfs_select_ref_head() since 'locked_ref' is no longer NULL but it's ERR_PTR(-EAGAIN), and then we do: spin_lock(&locked_ref->lock); against a ERR_PTR(-EAGAIN) value, generating an invalid pointer dereference. Fix this by ensuring that 'locked_ref' is set to NULL when btrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count' as well, to prevent infinite looping. We do this by doing a goto to the bottom of the loop that already sets 'locked_ref' to NULL and does a cond_resched(), with an increment to 'count' right before the goto. These measures were in place before the refactoring in commit 0110a4c43451 ("btrfs: refactor __btrfs_run_delayed_refs loop") but were unintentionally lost afterwards.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.18%

7.5th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 0110a4c43451533de1ea1bbdc57b5d452f9d8b25, < c372ca227e16bace86f1df1fa4ae6849e2fcfa28; >= 0110a4c43451533de1ea1bbdc57b5d452f9d8b25, < a71143590ce9764dbcb47617647592ff8b4d48bc; >= 0110a4c43451533de1ea1bbdc57b5d452f9d8b25, < 65770111a2d47c2b15e20b2ba92bb12198f289d4; >= 0110a4c43451533de1ea1bbdc57b5d452f9d8b25, < 015dc4a1e0c2cba551d4620eba13d26d5081dc34; >= 0110a4c43451533de1ea1bbdc57b5d452f9d8b25, < ba9fa2ff5981589bb49094d3358c339b37c47f53; >= 0110a4c43451533de1ea1bbdc57b5d452f9d8b25, < 3b15d02be05e74321adb1e0ae0cb4ccfba7c6cb1; >= 0110a4c43451533de1ea1bbdc57b5d452f9d8b25, < 9faa6b69ad73f03c7bde53e07d75a28822dc9a1a; >= 0110a4c43451533de1ea1bbdc57b5d452f9d8b25, < 486f8298b6188ff11ef1f4be7f1d5d2e4d1b1fae
Linux	Linux	4.20

References

Timeline

Published: Aug 15, 2026
Last Modified: Aug 17, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-74321?

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs() In the beginning of the loop, we try to obtain a locked delayed ref head, if 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(), which can return an error pointer. If the error pointer is -EAGAIN we do a continue and go back to the beginning of the loop, which will not try again to call btrfs_select_ref_head() since 'locked_ref' is no longer NULL but it's ERR_PTR(-EAGAIN), and then we do: spin_lock(&locked_ref->lock); against a ERR_PTR(-EAGAIN) value, generating an invalid pointer dereference. Fix this by ensuring that 'locked_ref' is set to NULL when btrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count' as well, to prevent infinite looping. We do this by doing a goto to the bottom of the loop that already sets 'locked_ref' to NULL and does a cond_resched(), with an increment to 'count' right before the goto. These measures were in place before the refactoring in commit 0110a4c43451 ("btrfs: refactor __btrfs_run_delayed_refs loop") but were unintentionally lost afterwards.

How severe is CVE-2026-74321?

CVE-2026-74321 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.18% probability of exploitation in the next 30 days.

How do I fix CVE-2026-74321?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

How Strix Helps

Related CVEs from 2026

View all 2026CVEs →