Critical· 9.4official fix available
CVE-2025-40099
A flaw in the Linux kernel's handling of SMB server replies can cause memory errors when processing malformed data. This occurs when a server sends an invalid response during a specific file system referral request.
publishedOct 30, 2025
last modifiedJul 30, 2026
sourcesNVD
severity · cvss
9.4
critical · how bad it is
exploitation · epss
<1%
31th percentile · chance of exploitation in 30 days
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →
auto-deletes from the system
counting…on Aug 29, 2026
An official fix is available, so this entry is kept for 30 days and then removed automatically.
01
Who is affected
Users running the Linux kernel that utilize the CIFS protocol for SMB connections.
02
Real-world impact
An attacker controlling a malicious SMB server could send specially crafted, invalid responses to trigger out-of-bounds memory access on a Linux system.
03
Why this severity
The critical score reflects that the vulnerability is remotely exploitable over a network without requiring user interaction or special privileges.
04
What to do about it
official fix available
recommended steps
- 01Update the Linux kernel to the version containing the fix for cifs: parse_dfs_referrals.
NVD-referenced vendor advisory
05
Timeline
- Oct 30, 2025 · Oct 30, 2025PublishedDisclosed and added to the National Vulnerability Database.
- Jul 30, 2026 · 6d agoAdvisory updatedThe NVD record was last revised.
- Jul 30, 2026 · 6d agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.
06
How it’s attacked
Attack vectorNetwork (remote)
Attack complexityLow
Privileges requiredNone
User interactionNone needed
ScopeUnchanged
Confidentiality impactHigh
Integrity impactLow
Availability impactHigh
07
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →