VulnerabilityPublished 15 Aug 2026Updated 30 Oct 2026

CVE-2026-72379: Linux kernel · fs: refuse O_TMPFILE creation with an unmapped fsuid or fsgid

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in bac8fb0d60254846f3b56957435dcd870ae12948 : update Linux kernel when convenient.

Data as of 30 Oct 2026, 13:20 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Patch: Available – fixed in bac8fb0d60254846f3b56957435dcd870ae12948, a2038514e69371eb493083a6a897ed20fcbb8acb, 74365c6e367725728d5ce36d38ca116c9f77a254 +3

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 30 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 ≥ 8e5389132ab429604c1a2459b52f0c849a71cc61, < bac8fb0d60254846f3b56957435dcd870ae12948	Fixed in bac8fb0d60254846f3b56957435dcd870ae12948
LinuxLinux	Affected ≥ 8e5389132ab429604c1a2459b52f0c849a71cc61, < a2038514e69371eb493083a6a897ed20fcbb8acb	Fixed in a2038514e69371eb493083a6a897ed20fcbb8acb
LinuxLinux	Affected ≥ 8e5389132ab429604c1a2459b52f0c849a71cc61, < 74365c6e367725728d5ce36d38ca116c9f77a254	Fixed in 74365c6e367725728d5ce36d38ca116c9f77a254
LinuxLinux	Affected ≥ 8e5389132ab429604c1a2459b52f0c849a71cc61, < 539dce1144651f7976fa418e618b0b574bf15eeb	Fixed in 539dce1144651f7976fa418e618b0b574bf15eeb
LinuxLinux	Affected ≥ 8e5389132ab429604c1a2459b52f0c849a71cc61, < 503d0568a525b168d9aa5ca046ec72fc5477df84	Fixed in 503d0568a525b168d9aa5ca046ec72fc5477df84
LinuxLinux	Affected ≥ 8e5389132ab429604c1a2459b52f0c849a71cc61, < 47e434da476b5a8bcd1e6e52ab03c5ee7764ee78	Fixed in 47e434da476b5a8bcd1e6e52ab03c5ee7764ee78

AI-suggested

This vulnerability has been fixed in the Linux kernel by adding the missing fsuidgid_has_mapping() check in vfs_tmpfile(). Users should update to a Linux kernel version that includes the fix identified by commits bac8fb0d60254846f3b56957435dcd870ae12948, a2038514e69371eb493083a6a897ed20fcbb8acb, 74365c6e367725728d5ce36d38ca116c9f77a254, 539dce1144651f7976fa418e618b0b574bf15eeb, 503d0568a525b168d9aa5ca046ec72fc5477df84, or 47e434da476b5a8bcd1e6e52ab03c5ee7764ee78. No additional mitigation is required once patched.

Description

A vulnerability in the Linux kernel's handling of O_TMPFILE creation on idmapped mounts allows creation of temporary files with invalid ownership when the caller's fsuid or fsgid is not mapped into the filesystem. This issue was fixed by adding a check to refuse O_TMPFILE creation if the fsuid or fsgid is unmapped, preventing temporary files from being owned by invalid user or group IDs.

Impact

Without this fix, temporary files created with O_TMPFILE on idmapped mounts could be assigned invalid ownership (uid_t -1), potentially leading to inconsistent filesystem state or security policy violations related to file ownership. This undermines the filesystem's integrity guarantees regarding ownership representation. The impact is limited to environments using idmapped mounts where the caller's fsuid or fsgid is not covered by the idmapping. There is no indication of active exploitation in the wild.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 13:20 UTC

Technical details

References

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