ksmbd: use opener credentials for ADS I/O
The Linux kernel ksmbd server's alternate data stream reads and writes are affected in versions from 5.15.0 up to the fixed releases 6.6.160, 6.12.96, 6.18.39, and 7.1.4. CVSS rates it 9.8 (critical).
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Fix
- Fixed in 6.6.160, 6.12.96, 6.18.39, 7.1.4
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The ksmbd in-kernel SMB server component of the Linux kernel is affected. Reads and writes to alternate data streams could be checked against the credentials of the current task instead of those captured when the file handle was opened, which may lead to incorrect permission and security policy enforcement.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original 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.
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
Version range not reported
- Linux Linux
5.15
- KernelLinux
From 5.15.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.96; From 6.13.0 · fixed in 6.18.39; From 6.19.0 · fixed in 7.1.4
References 6
git.kernel.org
Questions about CVE-2026-64391
What does this mean?
The bug concerns how ksmbd, the kernel's SMB file server, reads and writes alternate data streams (ADS). The fix makes these operations use the credentials of the account that opened the file. ADS are stored as xattrs.Source: git.kernel.org
Am I affected, and how do I check?
Kernel versions from 5.15.0 up to but not including 6.6.160, 6.7.0 up to 6.12.96, 6.13.0 up to 6.18.39, and 6.19.0 up to 7.1.4 are listed as affected. To check a system, run uname -r and compare the result with these ranges, and confirm whether ksmbd is in use.Source: git.kernel.org
What should I do about it?
Upgrade to the fixed kernel for your release series: 6.6.160, 6.12.96, 6.18.39, or 7.1.4 or later.Source: git.kernel.org
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data