CVE-2026-99110 smb: client: fix heap overflow in cifs_do_set_acl()
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99110?
CVE-2026-99110 is a vulnerability in Linux, published on 28 Oct 2026.
Official 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).
Which versions are affected by CVE-2026-99110?
How do I fix CVE-2026-99110?
Upgrade to a fixed version.
Is CVE-2026-99110 being exploited?
There is no known exploitation of CVE-2026-99110 in the wild and no public exploit code.
Sources
Also known as AZL-111200, BELL-CVE-2026-99110, DEBIAN-CVE-2026-99110, GHSA-82wh-j3w4-q4wc, UBUNTU-CVE-2026-99110.