---
title: "CVE-2026-89637: Linux kernel smb client - Use After Free"
description: "Linux kernel smb client contains a use-after-free and buffer leak caused by improper handling of malformed secondary TRANSACT2 responses in cifs_check_trans2(), letting attackers cause memory corruption, exploit requires crafted malformed secondary T2 response."
url: https://panop.io/threat-heartbeat/CVE-2026-89637/
---

# CVE-2026-89637 Linux kernel smb client - Use After Free

Linux kernel smb client contains a use-after-free and buffer leak caused by improper handling of malformed secondary TRANSACT2 responses in cifs\_check\_trans2(), letting attackers cause memory corruption, exploit requires crafted malformed secondary T2 response.

CVSS base score 9.8 /10

Critical

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.58% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-89637)

## Details

Type

Use After Free

Impact

Use After Free, Denial Of Service

CVSS vector

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

Published

11 September 2026

Updated

15 October 2026

## Vendor fix

Update to the latest Linux kernel version containing the fix.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-89637](https://nvd.nist.gov/vuln/detail/CVE-2026-89637)
- [https://git.kernel.org/stable/c/5e6533a683f6a851158d9f33fb4ea8f4f25d7f84](https://git.kernel.org/stable/c/5e6533a683f6a851158d9f33fb4ea8f4f25d7f84)
- [https://git.kernel.org/stable/c/730d0bb19507b9e19c2fe5343109ac618e2fbce5](https://git.kernel.org/stable/c/730d0bb19507b9e19c2fe5343109ac618e2fbce5)
- [https://git.kernel.org/stable/c/9eed72e9534b10a6d9f8f5146feff3db53aebdba](https://git.kernel.org/stable/c/9eed72e9534b10a6d9f8f5146feff3db53aebdba)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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