CVE-2026-89634 (CVSS 9.1)

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix ALIGN() overflow in symlink_data() error context loop The check added by commit 7d9a7f1f96cd ("smb/client: fix possible infinite loop and oob read in symlink_data()") compared the post-ALIGN length against the remaining buffer, but ALIGN() itself can overflow: for ErrorDataLength near UINT32_MAX (e.g. 0xFFFFFFF9), ALIGN(x, 8) wraps to 0, so the subsequent bounds check passes, and the loop advances by zero bytes leaving 'p' pointing into stale data. Fix by checking the raw ErrorDataLength against the remaining space before applying ALIGN(), then checking again after. Since raw_len is bounded by the buffer, raw_len + 7 cannot overflow, so the second check is an exact post-alignment bounds guard.

Is your site exposed to CVE-2026-89634?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

9.1

CRITICAL

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

EPSS — Exploit Prediction

0.0070

Probability of exploitation

0.52%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

References

Other References

https://git.kernel.org/stable/c/1f824f61d1df52392eaf0b74dfa5659d724fde30 https://git.kernel.org/stable/c/2b4a25baa0b936fef6915c0459925077b324ecaf https://git.kernel.org/stable/c/62656b024efc21c3230eade1a847f25871c3d2bb https://git.kernel.org/stable/c/62a3025983c8c735a3c6fc85a59316f31b59af07 https://git.kernel.org/stable/c/657372ba6ea50b4474d2a6a610097eae8cd1f3e9 https://git.kernel.org/stable/c/b89d678f9eafcf8d74885983166ba26b40a04ea0

Frequently Asked Questions

What is CVE-2026-89634? +

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix ALIGN() overflow in symlink_data() error context loop The check added by commit 7d9a7f1f96cd ("smb/client: fix possible infinite loop and oob read in symlink_data()") compared the post-ALIGN length against the remaining buffer, but ALIGN() itself can overflow: for ErrorDataLength near UINT32_MAX (e.g. 0xFFFFFFF9), ALIGN(x, 8) wraps to 0, so the subsequent bounds check passes, and the loop advances by zero bytes leaving 'p' pointing into stale data. Fix by checking the raw ErrorDataLength against the remaining space before applying ALIGN(), then checking again after. Since raw_len is bounded by the buffer, raw_len + 7 cannot overflow, so the second check is an exact post-alignment bounds guard. It has a CVSS v3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-89634? +

CVE-2026-89634 has a CVSS v3.1 score of 9.1 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0070, placing it in the 1th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-89634? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

CVE-2026-89634