CVE-2026-64391
CRITICAL
Published Jul 25, 2026
Modified Jul 27, 2026
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.
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CVSS v3.1 Score
9.8
CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS — Exploit Prediction
0.0046
Probability of exploitation
0.37%
Percentile rank
EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.
References
Other References
Frequently Asked Questions
What is CVE-2026-64391? +
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. It has a CVSS v3.1 base score of 9.8 (CRITICAL).
How severe is CVE-2026-64391? +
CVE-2026-64391 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0046, placing it in the 0th percentile for exploitation probability.
How do I check if I'm vulnerable to CVE-2026-64391? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.
