CVE-2026-99110 (CVSS 7)

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix heap overflow in cifs_do_set_acl() cifs_set_acl() validates ACL size using posix_acl_xattr_size(): 4 + (count * 8) // 4-byte header + 8 bytes per ACE cifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS wire format into the same buffer: 6 + (count * 10) // 6-byte header + 10 bytes per ACE An ACL that passes the xattr-based check in cifs_set_acl() can overflow the heap when posix_acl_to_cifs() writes the larger CIFS format. Validate the CIFS format size against the remaining buffer space and USHRT_MAX before converting--data_count is __u16, so sizes above USHRT_MAX truncate the on-wire packet length, causing the server to apply a partial ACL. Replace MaxDataCount = 1000 with min(CIFSMaxBufSize, USHRT_MAX).

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CVSS v3.1 Score

7.0

HIGH

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0013

Probability of exploitation

0.03%

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

https://git.kernel.org/stable/c/1dac61e2c29d1a71784604b48cf3b1234a65ec29 https://git.kernel.org/stable/c/596b4062e6c75bdd85a7f2b7f2087a872dc420ac https://git.kernel.org/stable/c/68652afb9b9adf70125971abee9b95341e042249 https://git.kernel.org/stable/c/9312a00215602ba028495ef3fa00fb84af0478e0 https://git.kernel.org/stable/c/d96f3365ce61c5f39602955af43c8174548dee98

Frequently Asked Questions

What is CVE-2026-99110? +

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix heap overflow in cifs_do_set_acl() cifs_set_acl() validates ACL size using posix_acl_xattr_size(): 4 + (count * 8) // 4-byte header + 8 bytes per ACE cifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS wire format into the same buffer: 6 + (count * 10) // 6-byte header + 10 bytes per ACE An ACL that passes the xattr-based check in cifs_set_acl() can overflow the heap when posix_acl_to_cifs() writes the larger CIFS format. Validate the CIFS format size against the remaining buffer space and USHRT_MAX before converting--data_count is __u16, so sizes above USHRT_MAX truncate the on-wire packet length, causing the server to apply a partial ACL. Replace MaxDataCount = 1000 with min(CIFSMaxBufSize, USHRT_MAX). It has a CVSS v3.1 base score of 7.0 (HIGH).

How severe is CVE-2026-99110? +

CVE-2026-99110 has a CVSS v3.1 score of 7.0 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0013, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-99110? +

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.

CVE-2026-99110