High 8.6Published Apr 24, 2026

CVE-2026-31611ksmbd: require 3 sub-authorities before reading sub_auth[2]

Updated under an hour ago (Oct 28, 2026, 3:20 AM ET)

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It affects Linux and 2 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

In the Linux kernel, the following vulnerability has been resolved: ksmbd: require 3 sub-authorities before reading sub_auth[2] parse_dacl() compares each ACE SID against sid_unix_NFS_mode and on match reads sid.sub_auth[2] as the file mode. If sid_unix_NFS_mode is the prefix S-1-5-88-3 with num_subauth = 2 then compare_sids() compares only min(num_subauth, 2) sub-authorities so a client SID with num_subauth = 2 and sub_auth = {88, 3} will match. If num_subauth = 2 and the ACE is placed at the very end of the security descriptor, sub_auth[2] will be 4 bytes past end_of_acl. The out-of-band bytes will then be masked to the low 9 bits and applied as the file's POSIX mode, probably not something that is good to have happen. Fix this up by forcing the SID to actually carry a third sub-authority before reading it at all.

CVSS: 8.6 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before cf2148b880fb7c0fcd727202dbc4fd5d6998b9c2; from e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before b5b5d5936a50497fb151c0b122899a6894721c2b; from e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 08f9e6d899b5c834bbcc239eae1bed58d9b15d2c; from e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before d2454f4a002d08560a60f214f392e6491cf11560; from e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 46bbcd3ebfb3549c8da1838fc4493e79bd3241e7; from e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a; from e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 53370cf9090777774e07fd9a8ebce67c6cc333ab	CNA record
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem siemens:simatic_s7_1500_tm_mfp_gnu_linux_subsystem (from the name)	all versions	CISA ADP
linux linux_kernel linux:linux_kernel	from 5.15 before 6.6.136; from 6.7 before 6.12.83; from 6.13 before 6.18.24; from 6.19 before 6.19.14; from 7.0 before 7.0.1	NVD

References

References

https://git.kernel.org/stable/c/cf2148b880fb7c0fcd727202dbc4fd5d6998b9c2
https://git.kernel.org/stable/c/b5b5d5936a50497fb151c0b122899a6894721c2b	patch
https://git.kernel.org/stable/c/08f9e6d899b5c834bbcc239eae1bed58d9b15d2c	patch
https://git.kernel.org/stable/c/d2454f4a002d08560a60f214f392e6491cf11560	patch
https://git.kernel.org/stable/c/46bbcd3ebfb3549c8da1838fc4493e79bd3241e7	patch
https://git.kernel.org/stable/c/9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a	patch
https://git.kernel.org/stable/c/53370cf9090777774e07fd9a8ebce67c6cc333ab	patch
https://cert-portal.siemens.com/productcert/html/ssa-784472.html

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.