Unknown

CVE-2026-89595 — fsnotify: Fix stale object mask after concurrent mark updates

In the Linux kernel, the following vulnerability has been resolved: fsnotify: Fix stale object mask after concurrent mark updates When a mark gets a new event bit, fanotify and inotify may avoid recalculating the object mask if the cached aggregate already contains that bit. This is racy with a recalculation triggered by a concurrent update to another mark on the same connector. The concurrent scan can read the mark before the new bit is added, while the updater reads the old aggregate before that scan publishes its result. The updater then skips recalculation and the scan publishes a mask without the bit, leaving the object mask stale after both updates complete. This can be reproduced with two fanotify groups watching the same inode: one thread removes FAN_MODIFY from one existing mark while another thread adds FAN_MODIFY to the other mark. After both fanotify_mark() calls return, writes can fail to produce FAN_MODIFY for the group whose mark now contains the bit. This was reproduced on an unmodified v6.12.95 kernel. The equivalent inotify interleaving loses IN_MODIFY events. For normal fanotify additions, recalculate whenever the raw mark mask changes. The normal mask is not cleared asynchronously, so an unchanged addition cannot introduce missing interest. Always recalculate ignore-mask updates because FS_MODIFY handling may clear the ignore mask without taking mark->lock, making snapshot comparisons unreliable. Always recalculate after updating an existing inotify watch. Its replace path temporarily sets mark->mask to zero, so a concurrent scan can observe zero even when the old and final masks are equal. Assigning the replacement mask directly would avoid the transient zero, but existing-watch updates are infrequent, so unconditional recalculation is simpler.

Published Sep 11, 2026 · Updated Oct 19, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+2

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.22%

ahead of 11% of scored CVEs · Oct 24, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 63c882a05416e18de6fb59f7dd6da48f3bbe8273 and < 27d172b60eeca5c8fd51b246f9fb959067cf102b≥ 63c882a05416e18de6fb59f7dd6da48f3bbe8273 and < 2f09f08d602647fc4e328fc27ecb4c3008d10338≥ 63c882a05416e18de6fb59f7dd6da48f3bbe8273 and < de75382d6e354b2b055df4896d12a91969f12090≥ 63c882a05416e18de6fb59f7dd6da48f3bbe8273 and < 343ae18e960f6c5f1d34d58a69750c62cd463228≥ 63c882a05416e18de6fb59f7dd6da48f3bbe8273 and < 92289e66639f62abc754c6f3bce5ead7e98e4ee2≥ 63c882a05416e18de6fb59f7dd6da48f3bbe8273 and < 947400af98b9e63841929d079a2c3ea0a8ba227b≥ 63c882a05416e18de6fb59f7dd6da48f3bbe8273 and < ac8d8b599d466a129122bded77db3d0f8b96b461≥ 63c882a05416e18de6fb59f7dd6da48f3bbe8273 and < e422777fdd4746de1109575c51e65038d4c5c1be and 1 more version 2.6.31	Vulnerable	CVE Program (cve.org) e CISA ADP

EPSS over time FIRST

Oct 15, 2026 → Oct 24, 2026 · 9 reading(s) · max 0.22%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 15, 2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Sep 11, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 19, 2026 – Oct 19, 2026
1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

10 on the record

github.com/advisories/GHSA-h76q-h94r-6qmf
GitHub Security Advisories
git.kernel.org/stable/c/27d172b60eeca5c8fd51b246f9fb959067cf102b
NIST National Vulnerability Database
git.kernel.org/stable/c/343ae18e960f6c5f1d34d58a69750c62cd463228
NIST National Vulnerability Database
git.kernel.org/stable/c/92289e66639f62abc754c6f3bce5ead7e98e4ee2
NIST National Vulnerability Database
git.kernel.org/stable/c/2f09f08d602647fc4e328fc27ecb4c3008d10338
NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2026-89595
GitHub Security Advisories
git.kernel.org/stable/c/e422777fdd4746de1109575c51e65038d4c5c1be
NIST National Vulnerability Database
git.kernel.org/stable/c/de75382d6e354b2b055df4896d12a91969f12090
NIST National Vulnerability Database
git.kernel.org/stable/c/ac8d8b599d466a129122bded77db3d0f8b96b461
NIST National Vulnerability Database
git.kernel.org/stable/c/947400af98b9e63841929d079a2c3ea0a8ba227b
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Unknown CVE-2026-99086 dm-integrity: validate the superblock on resume 2d
Unknown CVE-2026-99087 dm-integrity: fix NULL pointer dereference when the 'R' flag is used 2d
Unknown CVE-2026-99085 sched_ext: Fix CPU hotplug hang when a dying CPU's tasks sit in the BPF scheduler 2d
Unknown CVE-2026-99084 readdir: take no inode lock on an immutable directory 2d
Unknown CVE-2026-99080 fs: Free any excess xarray nodes in clear_inode() 2d
Critical CVE-2026-99079 net/mlx5e: Prevent stale XSK buffer release on refill retry 2d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-89595 is "fsnotify: Fix stale object mask after concurrent mark updates", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.22% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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