Live › vulnerability › CVE-2026-99110
Go to dashboardThe Linux kernel's SMB client (cifs) can write a CIFS ACL larger than the buffer it allocated when setting file ACLs, because the size check uses the POSIX xattr format rather than the larger CIFS wire format. The overflow is a kernel heap write, which can corrupt memory and may allow privilege escalation, and oversized ACLs can also truncate the packet so the server applies a partial ACL.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-28 11:32 UTC. All times on this page are UTC.
Systems that mount SMB/CIFS shares with the kernel cifs client and set ACLs on those shares are the ones that call the vulnerable path. Machines that do not mount CIFS shares, or that run kernels without the cifs module, can skip it. The sources do not say whether an attacker needs access to the share or a local account to trigger it.
No product ranges from the sources yet.
uname -r and compare it to the fixed release in the kernel stable branch.lsmod | grep cifs; systems that never mount SMB shares are not exposed.Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
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).
This page as .md · .json · in your agent: get_signal("CVE-2026-99110")
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