ksmbd: use opener credentials for ADS I/O

Answer in brief

CVE-2026-64391 records a Critical severity (CVSS 9.8) vulnerability in ksmbd: use opener credentials for ADS I/O. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 25, 2026Updated Sep 4, 2026Source checked Sep 20, 2026First seen by HOL Aug 5, 2026Material review Sep 4, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.8
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:o:linux:linux_kernel::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=f44158485826c076335d6860d35872271a83791d <a8f5d39971bbad9340d49cd41b0e2da9452a649d \|\| >=f44158485826c076335d6860d35872271a83791d <2b4592cea214683de0f2ce6f8c22c097fb0ea1ab \|\| >=f44158485826c076335d6860d35872271a83791d <52a56cf53ec834c44ac1b4d16d585f26613ee5ce \|\| >=f44158485826c076335d6860d35872271a83791d <baa5e094886fffa7e6272edcb5e08be5ce28262c	a8f5d39971bbad9340d49cd41b0e2da9452a649d, 2b4592cea214683de0f2ce6f8c22c097fb0ea1ab, 52a56cf53ec834c44ac1b4d16d585f26613ee5ce, baa5e094886fffa7e6272edcb5e08be5ce28262c
Linux/Linuxgeneric	5.15	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to a8f5d39971bbad9340d49cd41b0e2da9452a649d if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 4, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 5, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: use opener credentials for ADS I/O Alternate data streams are stored as xattrs. Unlike regular file I/O, their read and write paths therefore call VFS xattr helpers which recheck inode permissions and LSM policy using the current task credentials. Run ADS I/O with the credentials captured when the SMB handle was opened.

Quoted source text, attributed separately from HOL analysis.