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OpenAdvisories
Medium · 5.9 Public exploit CVE-2025-26466 EUVD-2025-5920GHSA-m92w-x6j2-5gc5

Openssh: denial-of-service in openssh

Published Feb 28, 2025 · Updated Nov 5, 2026 · Assigned by redhat

Vendor: Red Hat Product: Red Hat Enterprise Linux 10 Product: Red Hat Enterprise Linux 6 Product: Red Hat Enterprise Linux 7 Product: Red Hat Enterprise Linux 8 Product: Red Hat Enterprise Linux 9 Product: Red Hat OpenShift Container Platform 4 Package: openssh Package: openssh Package: openssh Package: openssh Platform: Linux Ecosystem: Alpine Ecosystem: Azure Linux Ecosystem: Debian Ecosystem: Ubuntu

Description

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 products

VendorProductAffectedFixed
— OpenSSH 9.5p1 – ≤ 9.9p1 —
Red Hat Red Hat Enterprise Linux 10 — —
Red Hat Red Hat Enterprise Linux 9 — —
Red Hat Red Hat Enterprise Linux 6 — —
Red Hat Red Hat Enterprise Linux 7 — —
Red Hat Red Hat Enterprise Linux 8 — —
Red Hat Red Hat OpenShift Container Platform 4 — —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

Debian

Security tracker ↗
ReleasePackageFixed inAdvisory
Debian 14 openssh 1:9.9p2-1 —
Debian 13 openssh 1:9.9p2-1 —

Ubuntu

Security tracker ↗
ReleasePackageFixed inAdvisory
Ubuntu 24.04 LTS openssh 1:9.6p1-3ubuntu13.8 USN-7270-1
Ubuntu 22.04 LTS openssh 1:8.9p1-3ubuntu0.11 USN-7270-1
Ubuntu 20.04 LTS openssh 1:8.2p1-4ubuntu0.12 USN-7270-1

Red Hat

Security tracker ↗
ReleasePackageFixed inAdvisory
RHEL 10 openssh +5 9.9p1-7.el10_0 RHBA-2025:6305
RHEL 9 openssh +4 8.7p1-45.el9 RHSA-2025:6993
RHEL 9 pam_ssh_agent_auth 0.10.4-5.45.el9 RHSA-2025:6993

SUSE

Security tracker ↗
ReleasePackageFixed inAdvisory
SLES 15 SP6 openssh 9.6p1-150600.6.15.2 SUSE-SU-2025:0585-1
SLES 15 SP6 openssh-askpass-gnome 9.6p1-150600.6.15.1 SUSE-SU-2025:0585-1
Show 2 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLE Micro 6.1 openssh 9.6p1-slfo.1.1_2.1 SUSE-SU-2025:20226-1
SLE Micro 6.0 openssh 9.6p1-3.1 SUSE-SU-2025:20160-1

openSUSE

Security tracker ↗
ReleasePackageFixed inAdvisory
openSUSE Tumbleweed openssh 9.9p2-1.1 openSUSE-SU-2025:14820-1
openSUSE Leap 15.6 openssh 9.6p1-150600.6.15.2 SUSE-SU-2025:0585-1
openSUSE Leap 15.6 openssh-askpass-gnome 9.6p1-150600.6.15.1 SUSE-SU-2025:0585-1

Alpine

Security tracker ↗
ReleasePackageFixed inAdvisory
Alpine v3.24 openssh 9.9_p2-r0 —
Alpine v3.23 openssh 9.9_p2-r0 —
Alpine v3.22 openssh 9.9_p2-r0 —
Alpine v3.21 openssh 9.9_p2-r0 —
Alpine v3.20 openssh 9.7_p1-r5 —
Show 1 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Alpine v3.19 openssh 9.6_p1-r2 —

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 openssh 9.8p1-3 —

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

GitHub 5 repositories

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

Advisories 17

References