In the Linux kernel, the following vulnerability has been resolved:
smb: client: validate the whole DACL before rewriting it in cifsacl
build_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a
server-supplied dacloffset and then use the incoming ACL to rebuild the
chmod/chown security descriptor.
The original fix only checked that the struct smb_acl header fits before
reading dacl_ptr->size or dacl_ptr->num_aces. That avoids the immediate
header-field OOB read, but the rewrite helpers still walk ACEs based on
pdacl->num_aces with no structural validation of the incoming DACL body.
A malicious server can return a truncated DACL that still contains a
header, claims one or more ACEs, and then drive
replace_sids_and_copy_aces() or set_chmod_dacl() past the validated
extent while they compare or copy attacker-controlled ACEs.
Factor the DACL structural checks into validate_dacl(), extend them to
validate each ACE against the DACL bounds, and use the shared validator
before the chmod/chown rebuild paths. parse_dacl() reuses the same
validator so the read-side parser and write-side rewrite paths agree on
what constitutes a well-formed incoming DACL.
Published: 2026-05-01
CVSS: 8.8
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Download CVE-2026-31709 POC (Proof-of-Concept) here:
Tip: Download official Tor Browser at https://www.torproject.org/download/ to access .onion links.
https://hokyo.gr/poc-250-cve-2026-24118/
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