VulnerabilityPublished 4 Sep 2025Updated 30 Oct 2026

CVE-2025-38709: Linux kernel · loop: Avoid updating block size under exclusive owner

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in b928438cc87c0bf7ae078e4b7b6e14261e84c5c5 : update Linux kernel when convenient.

Data as of 30 Oct 2026, 12:33 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Patch: Available – fixed in b928438cc87c0bf7ae078e4b7b6e14261e84c5c5, 46034518cae95db4abfde990c9ca1a0751855072, 457d2c5e112fd08dc1039b1ae39a83ec1782360d +3

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Sep 2025
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 ≥ 89e4fdecb51cf5535867026274bc97de9480ade5, < b928438cc87c0bf7ae078e4b7b6e14261e84c5c5	Fixed in b928438cc87c0bf7ae078e4b7b6e14261e84c5c5
LinuxLinux	Affected ≥ 89e4fdecb51cf5535867026274bc97de9480ade5, < 46034518cae95db4abfde990c9ca1a0751855072	Fixed in 46034518cae95db4abfde990c9ca1a0751855072
LinuxLinux	Affected ≥ 89e4fdecb51cf5535867026274bc97de9480ade5, < 457d2c5e112fd08dc1039b1ae39a83ec1782360d	Fixed in 457d2c5e112fd08dc1039b1ae39a83ec1782360d
LinuxLinux	Affected ≥ 89e4fdecb51cf5535867026274bc97de9480ade5, < 139a000d20f2f38ce34296feddd641d730fe1c08	Fixed in 139a000d20f2f38ce34296feddd641d730fe1c08
LinuxLinux	Affected ≥ 89e4fdecb51cf5535867026274bc97de9480ade5, < 7e49538288e523427beedd26993d446afef1a6fb	Fixed in 7e49538288e523427beedd26993d446afef1a6fb
LinuxLinux	Affected ≥ 89e4fdecb51cf5535867026274bc97de9480ade5, < 5d67b30aefeb7a949040bbb1b4e3b84c5d29a624	Fixed in 5d67b30aefeb7a949040bbb1b4e3b84c5d29a624

Description

In the Linux kernel, the following vulnerability has been resolved: loop: Avoid updating block size under exclusive owner Syzbot came up with a reproducer where a loop device block size is changed underneath a mounted filesystem. This causes a mismatch between the block device block size and the block size stored in the superblock causing confusion in various places such as fs/buffer.c. The particular issue triggered by syzbot was a warning in __getblk_slow() due to requested buffer size not matching block device block size. Fix the problem by getting exclusive hold of the loop device to change its block size. This fails if somebody (such as filesystem) has already an exclusive ownership of the block device and thus prevents modifying the loop device under some exclusive owner which doesn't expect it.

References

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