Openssh: denial-of-service in openssh
Priority MEDIUM 60CWE-770Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-770.
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 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.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.38682 98th percentileScored 2026-11-07
Fix Fixed Red Hat: 1 advisory
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | OpenSSH | 9.5p1 – 9.9p1 | — | No fix listed | CNA |
| Red Hat | Red Hat Enterprise Linux 10 | — | 9.9p1-7.el10_0 | Patch available | CNA |
| Red Hat | Red Hat Enterprise Linux 9 | — | 8.7p1-45.el9 | Patch available | CNA |
| Red Hat | Red Hat Enterprise Linux 9 | — | 8.7p1-45.el9 | Patch available | CNA |
| Red Hat | Red Hat Enterprise Linux 6 | — | — | Not affected | CNA |
| Red Hat | Red Hat Enterprise Linux 7 | — | — | Not affected | CNA |
| Red Hat | Red Hat Enterprise Linux 8 | — | — | Not affected | CNA |
| Red Hat | Red Hat OpenShift Container Platform 4 | — | — | Not affected | CNA |
| Red Hat | Red Hat OpenShift Container Platform 4 | — | — | Not affected | CNA |
- OpenSSH Vendor— Affected 9.5p1 – 9.9p1 Fixed in — No fix listed CNA
- Red Hat Enterprise Linux 10 VendorRed Hat Affected — Fixed in 9.9p1-7.el10_0 Patch available CNA
- Red Hat Enterprise Linux 9 VendorRed Hat Affected — Fixed in 8.7p1-45.el9 Patch available CNA
- Red Hat Enterprise Linux 9 VendorRed Hat Affected — Fixed in 8.7p1-45.el9 Patch available CNA
- Red Hat Enterprise Linux 6 VendorRed Hat Affected — Fixed in — Not affected CNA
- Red Hat Enterprise Linux 7 VendorRed Hat Affected — Fixed in — Not affected CNA
- Red Hat Enterprise Linux 8 VendorRed Hat Affected — Fixed in — Not affected CNA
- Red Hat OpenShift Container Platform 4 VendorRed Hat Affected — Fixed in — Not affected CNA
- Red Hat OpenShift Container Platform 4 VendorRed Hat Affected — Fixed in — Not affected CNA
CPE configurations NVD · 14
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:openbsd:openssh:9.5:p1:*:*:*:*:*:* | 9.5 p1 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:9.6:-:*:*:*:*:*:* | 9.6 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:9.6:p1:*:*:*:*:*:* | 9.6 p1 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:9.7:-:*:*:*:*:*:* | 9.7 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:9.7:p1:*:*:*:*:*:* | 9.7 p1 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:9.8:-:*:*:*:*:*:* | 9.8 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:9.8:p1:*:*:*:*:*:* | 9.8 p1 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:9.9:-:*:*:*:*:*:* | 9.9 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:9.9:p1:*:*:*:*:*:* | 9.9 p1 | Vulnerable | OpenBSD |
| cpe:2.3:o:canonical:ubuntu_linux:24.04:*:*:*:lts:*:*:* | 24.04 | Vulnerable | Canonical |
- cpe:2.3:a:openbsd:openssh:9.5:p1:*:*:*:*:*:* Versions 9.5 p1 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:9.6:-:*:*:*:*:*:* Versions 9.6 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:9.6:p1:*:*:*:*:*:* Versions 9.6 p1 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:9.7:-:*:*:*:*:*:* Versions 9.7 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:9.7:p1:*:*:*:*:*:* Versions 9.7 p1 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:9.8:-:*:*:*:*:*:* Versions 9.8 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:9.8:p1:*:*:*:*:*:* Versions 9.8 p1 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:9.9:-:*:*:*:*:*:* Versions 9.9 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:9.9:p1:*:*:*:*:*:* Versions 9.9 p1 Vulnerable ·OpenBSD
- cpe:2.3:o:canonical:ubuntu_linux:24.04:*:*:*:lts:*:*:* Versions 24.04 Vulnerable ·Canonical
Show 4 more CPE
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:canonical:ubuntu_linux:24.10:*:*:*:*:*:*:* | 24.10 | Vulnerable | Canonical |
| cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* | 11.0 | Vulnerable | Debian |
| cpe:2.3:o:debian:debian_linux:12.0:*:*:*:*:*:*:* | 12.0 | Vulnerable | Debian |
| cpe:2.3:o:debian:debian_linux:13.0:*:*:*:*:*:*:* | 13.0 | Vulnerable | Debian |
- cpe:2.3:o:canonical:ubuntu_linux:24.10:*:*:*:*:*:*:* Versions 24.10 Vulnerable ·Canonical
- cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* Versions 11.0 Vulnerable ·Debian
- cpe:2.3:o:debian:debian_linux:12.0:*:*:*:*:*:*:* Versions 12.0 Vulnerable ·Debian
- cpe:2.3:o:debian:debian_linux:13.0:*:*:*:*:*:*:* Versions 13.0 Vulnerable ·Debian
Remediation
Red Hat 1 advisory
- RHSA-2025:6993 Released 2025-05-13 · Red Hat rating Moderateopenssh security update
- Red Hat Enterprise Linux AppStream (v. 9) openssh-askpass-8.7p1-45.el9, pam_ssh_agent_auth-0.10.4-5.45.el9
- Red Hat Enterprise Linux BaseOS (v. 9) openssh-8.7p1-45.el9, openssh-clients-8.7p1-45.el9, openssh-keycat-8.7p1-45.el9 +1
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux AppStream (v. 10) | Fixed | — |
| Red Hat Enterprise Linux AppStream (v. 9) | Fixed | RHSA-2025:6993 |
| Red Hat Enterprise Linux BaseOS (v. 10) | Fixed | — |
| Red Hat Enterprise Linux BaseOS (v. 9) | Fixed | RHSA-2025:6993 |
Not affected: 4 products
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat OpenShift Container Platform 4
Timeline
- 2026-10-02 Threatist record created from CVE-2025-26466
- 2026-10-03 Alias added: GHSA-m92w-x6j2-5gc5
- 2026-10-08 Affected versions changed · Red Hat
- 2026-10-08 Fix available: openssh@0:9.9p1-7.el10_0 · CNA
- 2026-10-08 1 new reference · CNA
- 2026-10-09 Fix available: RHSA-2025:6993 · Red Hat
- 2026-10-09 Fix available: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 10) +1 · Red Hat
- 2026-10-09 Fix available: openssh@0:8.7p1-45.el9 · CNA
- 2026-10-09 1 new reference · CNA
- 2026-10-21 Affected versions changed · CNA
References
Advisory 10
- RHBA-2025:6305
- RHSA-2025:6993
- https://access.redhat.com/security/cve/CVE-2025-26466
- https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt
- https://bugzilla.suse.com/show_bug.cgi?id=1237041
- https://security-tracker.debian.org/tracker/CVE-2025-26466
- https://security.netapp.com/advisory/ntap-20250228-0002/
- https://ubuntu.com/security/CVE-2025-26466
- https://www.openwall.com/lists/oss-security/2025/02/18/1
- https://www.openwall.com/lists/oss-security/2025/02/18/4
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- TI-2019-03949 Out-of-bounds write in ESXi and Horizon DaaS KEVCVSS 3.1CRITICAL 9.8
- TI-2018-16080 A code execution vulnerability exists in the Stapler web framework used by Jenkins 2.153… KEVCVSS 3.1CRITICAL 9.8
Sources
- CVE-2025-26466 · CVE Program
- CVE-2025-26466 · NVD
- FIRST EPSS
- GHSA-m92w-x6j2-5gc5 · GitHub Advisory Database · CC BY 4.0
- CVE-2025-26466 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences