CVE-2026-89631
A critical flaw in the Linux kernel's SMB client could let a remote server trigger an out-of-bounds read by sending a tree-connect response with an undersized byte count. Data from the affected kernel object could then be exposed through `/proc/fs/cifs/DebugData`. The NVD says the issue has been resolved by rejecting responses containing fewer than two bytes.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
No affected products are identified by CPE in the supplied data. The flaw concerns the Linux kernel SMB client, but the data does not list affected versions or distributions.
Real-world impact
A malicious SMB server could cause the Linux SMB client to read beyond the intended memory boundary and expose kernel memory contents to an unprivileged local user.
Why this severity
Critical — CVSS 9.1. The attack can be initiated remotely over the network without prior privileges or user interaction, and the CVSS scoring indicates high confidentiality and availability impact.
What to do about it
- 01Upgrade the Linux kernel to a version that includes the NVD-described fix, which rejects SMB tree-connect responses with a ByteCount below two.
NVD description of the resolved Linux-kernel fix
Timeline
- Sep 11, 2026 · 2d agoPublishedDisclosed and added to the National Vulnerability Database.
- Sep 13, 2026 · 7h agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.