VulnerabilityPublished 17 Sep 2026Updated 21 Oct 2026

CVE-2026-90263: Linux kernel · btrfs: check if root is readonly when setting posix acl

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in dc3a6e90a0a6350a6d43fed9f005f54171809580 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 13:47 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in dc3a6e90a0a6350a6d43fed9f005f54171809580, d5602f96ff1e266f069b4d0d94f441050e057e06, ce8103676f4d4b13e1f087fcfb34f80774d30be2 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 353c2ea735e4b54fb6250861e67b51b1bcb47198, < dc3a6e90a0a6350a6d43fed9f005f54171809580	Fixed in dc3a6e90a0a6350a6d43fed9f005f54171809580
LinuxLinux	Affected ≥ 353c2ea735e4b54fb6250861e67b51b1bcb47198, < d5602f96ff1e266f069b4d0d94f441050e057e06	Fixed in d5602f96ff1e266f069b4d0d94f441050e057e06
LinuxLinux	Affected ≥ 353c2ea735e4b54fb6250861e67b51b1bcb47198, < ce8103676f4d4b13e1f087fcfb34f80774d30be2	Fixed in ce8103676f4d4b13e1f087fcfb34f80774d30be2
LinuxLinux	Affected ≥ 353c2ea735e4b54fb6250861e67b51b1bcb47198, < 20b2c2f3316e82a76ae3358c0bd45824f50f3fd5	Fixed in 20b2c2f3316e82a76ae3358c0bd45824f50f3fd5
LinuxLinux	Affected ≥ 353c2ea735e4b54fb6250861e67b51b1bcb47198, < 01c2f41fc441f75b3f9326443372faceb1cb6638	Fixed in 01c2f41fc441f75b3f9326443372faceb1cb6638
LinuxLinux	Affected =5.2	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: check if root is readonly when setting posix acl For a filesystem which has btrfs read-only property set to true, all write operations including acl and xattr should be denied. However, acl can still be set even if btrfs ro property is true. This happens because no function on the set_acl code path checks the root is readonly or not. It was checked in btrfs_setxattr_trans() but got removed in commit 353c2ea735e4 ("btrfs: remove redundant readonly root check in btrfs_setxattr_trans") That commit didn't check if all the callers properly check the root's read-only flag. A previous fix is commit b51111271b03 ("btrfs: check if root is readonly while setting security xattr"). Always check if the root is read-only before performing the set acl operation.

References

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