Resource exhaustion in OpenBSD OpenSSH
CVE-2025-26466
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.398 (98.6th percentile), scored .
Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 99th percentile — 98.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.398 · newest: 0.398 · change: 0.000
Affected products
- OpenBSD OpenSSH — versions 9.5, 9.6, 9.7
- Canonical Ubuntu Linux — versions 24.04, 24.10
- Debian Linux — versions 11.0, 12.0, 13.0
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat In-Vehicle Operating System 1
- Red Hat Openshift Container Platform 4
Weakness classification (CWE)
Public proof-of-concept exploits
- rxerium/CVE-2025-26466
- mrowkoob/CVE-2025-26466-msf
- acidboonrs/cve-2025-26466-openssh-poc
- tpirate/CVE-2025-26466
- Theshield-crack/wazuh-SIEM-with-ubuntu
- Theshield-crack/wazuh-SIEM-with-ubuntu-
- dolutech/patch-manual-CVE-2025-26465-e-CVE-2025-26466
- mosaicwang/myrpm
- nomi-sec/PoC-in-GitHub
- pawan-shivarkar/List-of-CVE-s-
References
- access.redhat.com/security/cve/CVE-2025-26466 (Third Party Advisory, vdb-entry)
- bugzilla.redhat.com/show_bug.cgi (issue-tracking, Issue Tracking)
- seclists.org/oss-sec/2025/q1/144
- www.qualys.com/2025/02/18/openssh-mitm-dos.txt (Third Party Advisory)
- af854a3a-2127-422b-91ae-364da2661108
- af854a3a-2127-422b-91ae-364da2661108
- af854a3a-2127-422b-91ae-364da2661108
- af854a3a-2127-422b-91ae-364da2661108 (Third Party Advisory)
- af854a3a-2127-422b-91ae-364da2661108 (Third Party Advisory)
- af854a3a-2127-422b-91ae-364da2661108 (Third Party Advisory)
Frequently asked questions
- What is CVE-2025-26466?
- CVE-2025-26466 is a medium-severity vulnerability in OpenBSD OpenSSH, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.9/10. Published 2025-02-28.
- How severe is CVE-2025-26466?
- Medium severity. CVSS v3 base score is 5.9 out of 10.
- Is CVE-2025-26466 known to be exploited?
- 15 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.