CVE-2026-99175: Linux Vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: fsnotify: prevent mark additions during connector teardown fsnotify_destroy_marks() keeps a reference to its current mark while it drops conn->lock to destroy the mark. This stabilizes the forward-walk cursor, but does not prevent a new mark from being inserted before it. For example, an inotify watch re-added after IN_IGNORED sorts before the old, detached mark for the same group. The walk can miss the replacement and then detach the entire connector from the object. The replacement is still on its group's marks_list and, for inotify, in the watch IDR. The group mutex no longer protects the connector's object from disappearing. An unprivileged fdinfo read racing the final detach can consequently call igrab(NULL): BUG: KASAN: null-ptr-deref in igrab+0x24/0x100 Write of size 4 at addr 0000000000000148 Call Trace: igrab+0x24/0x100 inotify_show_fdinfo+0x1dc/0x5e0 seq_show+0x397/0x690 Set a DESTROYING flag under conn->lock before starting the walk, and reject new marks on that connector with -ENOENT. The existing add-mark error paths undo the temporary group-list entry and the backend's watch allocation. Do not wait for teardown while holding the group mutex, which the destroyer needs. Once the old connector is detached, an add can install a fresh connector as before. This closes the insertion race for all object types using the common connector teardown, without changing the mark reference or SRCU lifetime rules.

Metrics

EPSS Probability

0.17%

5.9th 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	>= 6b3f05d24d355f50f3d9814304650fcab0efb482, < f7def717c06aea7004905e4d1568c3691ef9825d; >= 6b3f05d24d355f50f3d9814304650fcab0efb482, < da2f9aa89ef1b1fe7a7c6e1a8ddacd9c975e86aa; >= 6b3f05d24d355f50f3d9814304650fcab0efb482, < 587d80966dcce2824f13fd32dab83bf882acf66f; >= 6b3f05d24d355f50f3d9814304650fcab0efb482, < d28a460a2237220d9ccbdd3baac6eaead44e96cb; >= 6b3f05d24d355f50f3d9814304650fcab0efb482, < 61133f15773b907bada651a02d9c6d38eae37c48; >= 6b3f05d24d355f50f3d9814304650fcab0efb482, < 952501bfc6e5e654ac4a17ec9d90c1ec614bd9f1; >= 6b3f05d24d355f50f3d9814304650fcab0efb482, < 472589eacdf10b5f9bd10b333957ed5291b2544b; >= 6b3f05d24d355f50f3d9814304650fcab0efb482, < 36ebddca56b9d8993d6dc984fdecc748ee1f5e06
Linux	Linux	4.12

References

Timeline

Published: Oct 28, 2026
Last Modified: Oct 30, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-99175?

In the Linux kernel, the following vulnerability has been resolved: fsnotify: prevent mark additions during connector teardown fsnotify_destroy_marks() keeps a reference to its current mark while it drops conn->lock to destroy the mark. This stabilizes the forward-walk cursor, but does not prevent a new mark from being inserted before it. For example, an inotify watch re-added after IN_IGNORED sorts before the old, detached mark for the same group. The walk can miss the replacement and then detach the entire connector from the object. The replacement is still on its group's marks_list and, for inotify, in the watch IDR. The group mutex no longer protects the connector's object from disappearing. An unprivileged fdinfo read racing the final detach can consequently call igrab(NULL): BUG: KASAN: null-ptr-deref in igrab+0x24/0x100 Write of size 4 at addr 0000000000000148 Call Trace: igrab+0x24/0x100 inotify_show_fdinfo+0x1dc/0x5e0 seq_show+0x397/0x690 Set a DESTROYING flag under conn->lock before starting the walk, and reject new marks on that connector with -ENOENT. The existing add-mark error paths undo the temporary group-list entry and the backend's watch allocation. Do not wait for teardown while holding the group mutex, which the destroyer needs. Once the old connector is detached, an add can install a fresh connector as before. This closes the insertion race for all object types using the common connector teardown, without changing the mark reference or SRCU lifetime rules.

How severe is CVE-2026-99175?

Severity scoring for CVE-2026-99175 is pending analysis. The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-99175?

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.

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