Linux Kernel ksmbd SID Memory Leak on DACL Overflow
CVE-2026-64139 Published on July 19, 2026
ksmbd: fix SID memory leak in set_posix_acl_entries_dacl() on overflow
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix SID memory leak in set_posix_acl_entries_dacl() on overflow
Commit 299f962c0b02 ("ksmbd: use check_add_overflow() to prevent u16
DACL size overflow") added check_add_overflow() guards that break out
of the ACE-building loops in set_posix_acl_entries_dacl() when the
accumulated DACL size would wrap past 65535.
However, each iteration allocates a struct smb_sid via kmalloc_obj()
at the top of the loop and relies on the kfree(sid) call at the end
of the loop body (the 'pass_same_sid' label in the first loop, and
the explicit kfree at the tail of the second loop) to release it.
The newly introduced 'break' statements bypass those kfree() calls,
leaking the sid buffer every time an overflow is detected.
A malicious or malformed file with enough POSIX ACL entries to trip
the overflow check will leak one or more struct smb_sid allocations
on every request that touches the file's DACL, providing a trivial
kernel memory exhaustion vector.
Free sid before breaking out of the loops to plug the leak.
Products Associated with CVE-2026-64139
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Affected Versions
Linux:- Version 8d5729350b236896f51379588d9a690b7fafb8db and below 9d378e17c864da08c3a4df41dae92cfa6468b00a is affected.
- Version e1955a94b6f17f4b058afa955a6f187eb3ed7615 and below 519fb0a42ce5d7e46935577309fb282a5f2c6ea3 is affected.
- Version 5e7b8f3c539d69b2ed5f2408e2f75e68ce7eef43 and below 0e198f09cb2a554c04de0fea4e790f1250a943ca is affected.
- Version ef7902be3f215b6bf7babe4dc9dd9a7d57dad7a7 and below eced48cb08f07393a5ea770fdd1026452883c3ad is affected.
- Version 299f962c0b02d048fb45d248b4da493d03f3175d and below af92ee994cc7f7e83a41c2025f32257a2f82a7ef is affected.
- Version 41e53a773db6342ac9a689ee5ba635c31744c9f0 is affected.
- Version 6.1.175 and below 6.2 is affected.
- Version 6.6.136 and below 6.6.142 is affected.
- Version 6.12.84 and below 6.12.92 is affected.
- Version 6.18.25 and below 6.18.34 is affected.
- Version 7.0.2 and below 7.0.11 is affected.