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CVE-2026-97554

Linux: smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr()

Linux LinuxOperating systems
Open in ThreatlineRecord JSON
CVSS
NoneNot scored
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.20%Chance of exploitation activity in the next 30 days, higher than 9% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in604feb3e8141bf11f5afd48d36d401fee5af9536Also 33106019c3be57b5fc6411cfaad6d98214a51265, 2be31f252ade791b84f7164991f14436aed1d4b9 and 2 moreCVE List
Published25 Sep 2026Updated 21 Oct 2026CVE List

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

In the Linux kernel, the following vulnerability has been resolved:

smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr()

cifs_posix_to_fattr() ignores the return value of posix_info_parse(). When a malformed POSIX directory entry is encountered (e.g. invalid SID lengths from an untrusted server), posix_info_parse() returns -1 without populating the 'parsed' struct. The uninitialized stack memory in parsed.owner and parsed.group is then passed to sid_to_id(), which processes the garbage bytes and passes them to request_key() to construct a SID string, potentially leaking kernel stack contents to the userspace idmap daemon.

Fix this by checking the return value and skipping the SID-to-id mapping when parsing fails. The remaining fattr fields (timestamps, mode, etc.) are populated directly from the 'info' pointer so they are unaffected.

Text from CVE List

Affected versions 16

  • Linuxaffected: 9934430e2178d5164eb1ac91a9b092f9e7e64745 before 604feb3e8141bf11f5afd48d36d401fee5af9536CVE List
  • Linuxaffected: 9934430e2178d5164eb1ac91a9b092f9e7e64745 before 33106019c3be57b5fc6411cfaad6d98214a51265CVE List
  • Linuxaffected: 9934430e2178d5164eb1ac91a9b092f9e7e64745 before 2be31f252ade791b84f7164991f14436aed1d4b9CVE List
  • Linuxaffected: 9934430e2178d5164eb1ac91a9b092f9e7e64745 before c9a8b60ce140a68d172452f418137fc7ddbae7dbCVE List
  • Linuxaffected: 9934430e2178d5164eb1ac91a9b092f9e7e64745 before da6e25842431982d5a53cf00d925b98c690f4467CVE List
  • Linuxaffected: dd80b98bdf0a4b3206739f3513b0518f27a7b4efCVE List
  • Linuxaffected: d8e39c11f66125f49de55537a6efc8ecadf4a0f7CVE List
  • Linuxaffected: 5.8.17 before 5.9CVE List
  • Linuxaffected: 5.9.2 before 5.10CVE List
  • Linuxaffected: 5.10CVE List
  • Linuxunaffected: all versions before 5.10CVE List
  • Linuxunaffected: 6.6.160 through 6.6.*CVE List
  • Linuxunaffected: 6.12.114 through 6.12.*CVE List
  • Linuxunaffected: 6.18.57 through 6.18.*CVE List
  • Linuxunaffected: 7.2.7 through 7.2.*CVE List
  • Linuxunaffected: 7.3CVE List

References 5