What is CVE-2026-89631?

CVE-2026-89631 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.1 out of 10, affecting Linux kernel versions from 2.6.30 onward and patched in 6.18.51, 7.2.4 and 7.3-rc1. CVE-2026-89631 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-89631?

CVE-2026-89631 has a CVSS score of 9.1 out of 10, rated Critical severity. The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H.

Is there a patch available for CVE-2026-89631?

Yes, CVE-2026-89631 has been patched. Fixed versions include 6.18.51, 7.2.4 and 7.3-rc1. If you are running Linux kernel 2.6.30 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-89631 actively exploited?

CVE-2026-89631 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2026-89631

Critical

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject a tree connect response whose byte count is too small CIFSTCon() bounds its strnlen() over the byte area with the server's ByteCount minus two, which for ByteCount 0 or 1 goes negative as an int and converts to a huge size_t. The later subtraction wraps the __u16 bytes_left, and that is what bounds cifs_strndup_from_utf16(): a bound of up to 65535 against a ~16 KB cifs_req_poolp object runs off the end of the slab object, and the bytes reach userspace through tcon->nativeFileSystem in /proc/fs/cifs/DebugData. Reject a byte area too small for what the parser consumes. Two bytes is the least it can consume, and no conformant response carries fewer. The new trace point is the 129th smb_eio_trace entry, which __mode(byte) cannot represent, so the attribute goes with it.

Package Linux Kernel

Published 2026-09-11

Last modified 2026-09-13

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

9.1

out of 10

Critical

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

High

Vector string

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected versions

Linux kernel versions 2.6.30 and later are affected. Fixed in 6.18.51, 7.2.4, 7.3-rc1 and their respective stable series.

Affected from

≥ 2.6.30

Fixed in

✓ 6.18.51 6.18.x ✓ 7.2.4 7.2.x ✓ 7.3-rc1

References

3 total

Details

CVE ID CVE-2026-89631

Severity Critical

CVSS score 9.1 / 10

CVSS version 3.1

Published 2026-09-11

Modified 2026-09-13

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-89631?

CVE-2026-89631 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.1 out of 10 . It affects Linux kernel versions from 2.6.30 onward and has been patched in 6.18.51, 7.2.4 and 7.3-rc1. CVE-2026-89631 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-89631?

CVE-2026-89631 has a CVSS score of 9.1 out of 10, rated Critical severity (CVSS 3.1). The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H.
Is there a patch available for CVE-2026-89631?

Yes. CVE-2026-89631 has been patched. Fixed versions include 6.18.51, 7.2.4 and 7.3-rc1. If you are running Linux kernel 2.6.30 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-89631 actively exploited?

No. CVE-2026-89631 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.