CVE-2025-38709: Linux kernel · loop: Avoid updating block size under exclusive owner
Source GCVE Database
Not known to be exploited · CVSS 5.5 Medium · fixed in b928438cc87c0bf7ae078e4b7b6e14261e84c5c5 : update Linux kernel when convenient.
Data as of 30 Oct 2026, 16:33 UTC
Thin evidence
One scorer or none- Patch
- Available – fixed in b928438cc87c0bf7ae078e4b7b6e14261e84c5c5, 46034518cae95db4abfde990c9ca1a0751855072, 457d2c5e112fd08dc1039b1ae39a83ec1782360d +3
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation 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.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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
- nvd.nist.gov/vuln/detail/CVE-2025-38709 (opens in a new tab)
- git.kernel.org/stable/c/139a000d20f2f38ce34296feddd641d730fe1c08 (opens in a new tab)
- git.kernel.org/stable/c/457d2c5e112fd08dc1039b1ae39a83ec1782360d (opens in a new tab)
- git.kernel.org/stable/c/46034518cae95db4abfde990c9ca1a0751855072 (opens in a new tab)
- git.kernel.org/stable/c/5d67b30aefeb7a949040bbb1b4e3b84c5d29a624 (opens in a new tab)
- git.kernel.org/stable/c/7e49538288e523427beedd26993d446afef1a6fb (opens in a new tab)
- git.kernel.org/stable/c/b928438cc87c0bf7ae078e4b7b6e14261e84c5c5 (opens in a new tab)
- git.kernel.org/stable/c/ce8da5d13d8c2a7b30b2fb376a22e8eb1a70b8bb (opens in a new tab)