CVE-2025-40099: Linux kernel · cifs: parse_dfs_referrals: prevent oob on malformed input
Source GCVE Database
Not known to be exploited · CVSS 9.4 Critical.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:HExploitation evidence
Disclosed: evidence found.
CVE published 30 Oct 2025
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.
What to do
AI-suggested
A fix has been implemented in the Linux kernel to return an error (-EINVAL) on malformed DFS referral replies, preventing out-of-bounds memory access. Users should update their Linux kernel to a version that includes this fix. Patch status is not explicitly confirmed in the provided data; therefore, check the official Linux kernel advisories or vendor updates for the exact fixed versions and apply them accordingly.
Description
A critical vulnerability in the Linux kernel's CIFS client was resolved to prevent out-of-bounds (OOB) memory access caused by malformed input from malicious SMB servers. Specifically, invalid replies to FSCTL_DFS_GET_REFERRALS with improperly sized data or inconsistent referral counts could trigger OOB conditions. The fix involves returning an error (-EINVAL) when such malformed replies are detected, preventing OOB memory access.
References
- nvd.nist.gov/vuln/detail/CVE-2025-40099 (opens in a new tab)
- git.kernel.org/stable/c/15c73964da9df994302f579ed14ee5fdbce7a332 (opens in a new tab)
- git.kernel.org/stable/c/6447b0e355562a1ff748c4a2ffb89aae7e84d2c9 (opens in a new tab)
- git.kernel.org/stable/c/8bc4a8d39bac23d8b044fd3e2dbfd965f1d9b058 (opens in a new tab)
- git.kernel.org/stable/c/bb0f2e66e1ac043a5b238f5bcab4f26f3c317039 (opens in a new tab)
- git.kernel.org/stable/c/cfacc7441f760e4a73cc71b6ff1635261d534657 (opens in a new tab)