---
title: "CVE-2026-89554: Linux Kernel - Memory Corruption"
description: "Linux kernel contains a memory corruption vulnerability caused by uninitialized local_id in syncookie MP_JOIN reconstruction, letting off-path attackers corrupt subflow bookkeeping, exploit requires sending concurrent MP_JOIN SYNs."
url: https://panop.io/threat-heartbeat/CVE-2026-89554/
---

# CVE-2026-89554 Linux Kernel - Memory Corruption

Linux kernel contains a memory corruption vulnerability caused by uninitialized local\_id in syncookie MP\_JOIN reconstruction, letting off-path attackers corrupt subflow bookkeeping, exploit requires sending concurrent MP\_JOIN SYNs.

CVSS base score 8.2 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.60% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-89554)

## Details

Type

Memory Corruption

Impact

Denial Of Service

CVSS vector

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

Published

11 September 2026

Updated

15 October 2026

## Vendor fix

Update to the latest Linux kernel version with the fix applied.

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-2026-89554](https://nvd.nist.gov/vuln/detail/CVE-2026-89554)
- [https://git.kernel.org/stable/c/63cacb05e51a1c6e1349d2e593d00fd6ef43def4](https://git.kernel.org/stable/c/63cacb05e51a1c6e1349d2e593d00fd6ef43def4)
- [https://git.kernel.org/stable/c/954b5ea836eb118d188975ced803448537ab8479](https://git.kernel.org/stable/c/954b5ea836eb118d188975ced803448537ab8479)
- [https://git.kernel.org/stable/c/9df36a4846375a9b75bf42d77bfed216b0f366f9](https://git.kernel.org/stable/c/9df36a4846375a9b75bf42d77bfed216b0f366f9)
- [https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982](https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982)
- [https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba](https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba)
- [https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9](https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9)
- [https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326](https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326)
- [https://git.kernel.org/stable/c/4534e0eead692bb069ad1e6a5a245fc2e2078300](https://git.kernel.org/stable/c/4534e0eead692bb069ad1e6a5a245fc2e2078300)

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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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