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CVE-2026-31611

8.6 · HIGH

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…

Published Apr 24, 2026EPSS 0.54%

Overview

CVE-2026-31611 is a high-severity vulnerability. It was published on April 24, 2026 and has a CVSS 3.1 base score of 8.6 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.6, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/08f9e6d899b5c834bbcc239eae1bed58d9b15d2cRefgit.kernel.org/stable/c/46bbcd3ebfb3549c8da1838fc4493e79bd3241e7Refgit.kernel.org/stable/c/53370cf9090777774e07fd9a8ebce67c6cc333abRefgit.kernel.org/stable/c/9401f86a224f37b50e6a3ccf1d46a70d5ef8af0aRefgit.kernel.org/stable/c/b5b5d5936a50497fb151c0b122899a6894721c2bRefgit.kernel.org/stable/c/cf2148b880fb7c0fcd727202dbc4fd5d6998b9c2Refgit.kernel.org/stable/c/d2454f4a002d08560a60f214f392e6491cf11560

How CyberStrike helps

Frequently asked questions

What is CVE-2026-31611?

CVE-2026-31611 is a high-severity vulnerability. It was published on April 24, 2026 and has a CVSS 3.1 base score of 8.6 (HIGH).

How severe is CVE-2026-31611?

This vulnerability has a CVSS 3.1 base score of 8.6, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-31611?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-31611?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-31611 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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