---
id: CVE-2025-26466
title: A flaw was found in the OpenSSH package
summary: >-
  A flaw was found in the OpenSSH package. For each ping packet the SSH server
  receives, a pong packet is allocated in a memory buffer and stored in a queue
  of packages. It is only freed when the server/client key exchange has
  finished. A …
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-770
  - CWE-770
vendor: openbsd
product: openssh
affected:
  - openssh = 9.5
  - openssh = 9.6
  - openssh = 9.7
  - openssh = 9.8
  - openssh = 9.9
  - ubuntu_linux = 24.04
  - ubuntu_linux = 24.10
  - debian_linux = 11.0
  - debian_linux = 12.0
  - debian_linux = 13.0
published: '2025-02-28'
updated: '2026-06-25'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-26466'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2025-26466'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2345043'
    label: secalert@redhat.com
  - url: 'https://seclists.org/oss-sec/2025/q1/144'
    label: secalert@redhat.com
  - url: 'https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt'
    label: secalert@redhat.com
  - url: 'http://seclists.org/fulldisclosure/2025/Feb/18'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://seclists.org/fulldisclosure/2025/May/7'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://seclists.org/fulldisclosure/2025/May/8'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://bugzilla.suse.com/show_bug.cgi?id=1237041'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security-tracker.debian.org/tracker/CVE-2025-26466'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20250228-0002/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://ubuntu.com/security/CVE-2025-26466'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.openwall.com/lists/oss-security/2025/02/18/1'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.openwall.com/lists/oss-security/2025/02/18/4'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://www.vicarius.io/vsociety/posts/cve-2025-26466-detection-script-memory-consumption-vulnerability-in-openssh
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://www.vicarius.io/vsociety/posts/cve-2025-26466-mitigation-script-memory-consumption-vulnerability-in-openssh
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - exploit-available
epss: 0.39845
epssPercentile: 0.98575
ingestedAt: '2026-06-29T13:24:34.173Z'
exploits:
  github: 4
  githubRepos:
    - 'https://github.com/rxerium/CVE-2025-26466'
    - 'https://github.com/mrowkoob/CVE-2025-26466-msf'
    - 'https://github.com/tpirate/CVE-2025-26466'
  checkedAt: '2026-09-25T08:20:44.832Z'
exploitAvailable: true
---

## Overview

A flaw was found in the OpenSSH package. For each ping packet the SSH server receives, a pong packet is allocated in a memory buffer and stored in a queue of packages. It is only freed when the server/client key exchange has finished. A malicious client may keep sending such packages, leading to an uncontrolled increase in memory consumption on the server side. Consequently, the server may become unavailable, resulting in a denial of service attack.

## Affected

- `openssh = 9.5`
- `openssh = 9.6`
- `openssh = 9.7`
- `openssh = 9.8`
- `openssh = 9.9`
- `ubuntu_linux = 24.04`
- `ubuntu_linux = 24.10`
- `debian_linux = 11.0`
- `debian_linux = 12.0`
- `debian_linux = 13.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.