Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled
Priority HIGH 65CWE-390Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- High
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Partial Red Hat: 7 fixed, 3 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.
Summary
A vulnerability was found in OpenSSH when the VerifyHostKeyDNS option is enabled. A machine-in-the-middle attack can be performed by a malicious machine impersonating a legit server. This issue occurs due to how OpenSSH mishandles error codes in specific conditions when verifying the host key. For an attack to be considered successful, the attacker needs to manage to exhaust the client's memory resource first, turning the attack complexity high.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.07723 94th percentileScored 2026-11-07
Fix Partial Red Hat: 4 advisoriesRed Hat: 7 fixed, 3 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Total
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 | 6.8p1 – 9.9p1 | — | No fix listed | CNA |
| Red Hat | Red Hat Enterprise Linux 8 | — | 8.0p1-26.el8_10 | Patch available | CNA |
| Red Hat | Red Hat Enterprise Linux 8 | — | 8.0p1-26.el8_10 | 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 9.4 Extended Update Support | — | 8.7p1-38.el9_4.5 | Patch available | CNA |
| Red Hat | Red Hat Discovery 1.14 | — | 1.14.3-1748529279 | Patch available | CNA |
| Red Hat | Red Hat Enterprise Linux 10 | — | — | Not affected | CNA |
| Red Hat | Red Hat Enterprise Linux 6 | — | — | No fix listed | CNA |
| Red Hat | Red Hat Enterprise Linux 7 | — | — | No fix listed | CNA |
| Red Hat | Red Hat OpenShift Container Platform 4 | — | — | No fix listed | CNA |
- OpenSSH Vendor— Affected 6.8p1 – 9.9p1 Fixed in — No fix listed CNA
- Red Hat Enterprise Linux 8 VendorRed Hat Affected — Fixed in 8.0p1-26.el8_10 Patch available CNA
- Red Hat Enterprise Linux 8 VendorRed Hat Affected — Fixed in 8.0p1-26.el8_10 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 9.4 Extended Update Support VendorRed Hat Affected — Fixed in 8.7p1-38.el9_4.5 Patch available CNA
- Red Hat Discovery 1.14 VendorRed Hat Affected — Fixed in 1.14.3-1748529279 Patch available CNA
- Red Hat Enterprise Linux 10 VendorRed Hat Affected — Fixed in — Not affected CNA
- Red Hat Enterprise Linux 6 VendorRed Hat Affected — Fixed in — No fix listed CNA
- Red Hat Enterprise Linux 7 VendorRed Hat Affected — Fixed in — No fix listed CNA
- Red Hat OpenShift Container Platform 4 VendorRed Hat Affected — Fixed in — No fix listed CNA
CPE configurations NVD · 10
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:openbsd:openssh:*:*:*:*:*:*:*:* | 6.9 – 9.8 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:6.8:p1:*:*:*:*:*:* | 6.8 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:a:netapp:active_iq_unified_manager:-:*:*:*:*:vmware_vsphere:*:* | not specified by NVD | Vulnerable | NetApp |
| cpe:2.3:a:netapp:ontap:9:*:*:*:*:*:*:* | 9 | Vulnerable | NetApp |
| cpe:2.3:a:redhat:openshift_container_platform:4.0:*:*:*:*:*:*:* | 4.0 | Vulnerable | Red Hat |
| 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:redhat:enterprise_linux:9.0:*:*:*:*:*:*:* | 9.0 | Vulnerable | Red Hat |
- cpe:2.3:a:openbsd:openssh:*:*:*:*:*:*:*:* Versions 6.9 – 9.8 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:6.8:p1:*:*:*:*:*:* Versions 6.8 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:a:netapp:active_iq_unified_manager:-:*:*:*:*:vmware_vsphere:*:* Versions not specified by NVD Vulnerable ·NetApp
- cpe:2.3:a:netapp:ontap:9:*:*:*:*:*:*:* Versions 9 Vulnerable ·NetApp
- cpe:2.3:a:redhat:openshift_container_platform:4.0:*:*:*:*:*:*:* Versions 4.0 Vulnerable ·Red Hat
- 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:redhat:enterprise_linux:9.0:*:*:*:*:*:*:* Versions 9.0 Vulnerable ·Red Hat
Remediation
Red Hat 4 advisories
- RHSA-2025:16823 Released 2025-09-26 · Red Hat rating Moderateopenssh security update
- Red Hat Enterprise Linux AppStream (v. 8) openssh-askpass-8.0p1-26.el8_10
- Red Hat Enterprise Linux BaseOS (v. 8) openssh-8.0p1-26.el8_10, openssh-cavs-8.0p1-26.el8_10, openssh-clients-8.0p1-26.el8_10 +4
- RHSA-2025:8385 Released 2025-06-02 · Red Hat rating ModerateA Subscription Management tool for finding and reporting Red Hat product usage
- Red Hat Discovery 1.14 registry.redhat.io/discovery/discovery-server-rhel9, registry.redhat.io/discovery/discovery-ui-rhel9
- 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
Show 1 more Red Hat advisories
- RHSA-2025:3837 Released 2025-04-14 · Red Hat rating Moderateopenssh security update
- Red Hat Enterprise Linux AppStream EUS (v.9.4) openssh-askpass-8.7p1-38.el9_4.5, pam_ssh_agent_auth-0.10.4-5.38.el9_4.5
- Red Hat Enterprise Linux BaseOS EUS (v.9.4) openssh-8.7p1-38.el9_4.5, openssh-clients-8.7p1-38.el9_4.5, openssh-keycat-8.7p1-38.el9_4.5 +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 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat Discovery 1.14 | Fixed | RHSA-2025:8385 |
| Red Hat Enterprise Linux AppStream (v. 8) | Fixed | RHSA-2025:16823 |
| Red Hat Enterprise Linux AppStream (v. 9) | Fixed | RHSA-2025:6993 |
| Red Hat Enterprise Linux AppStream EUS (v.9.4) | Fixed | RHSA-2025:3837 |
| Red Hat Enterprise Linux BaseOS (v. 8) | Fixed | RHSA-2025:16823 |
| Red Hat Enterprise Linux BaseOS (v. 9) | Fixed | RHSA-2025:6993 |
| Red Hat Enterprise Linux BaseOS EUS (v.9.4) | Fixed | RHSA-2025:3837 |
Not affected: 2 products
- Red Hat Discovery 1.14
- Red Hat Enterprise Linux 10
Timeline
- 2026-10-02 Threatist record created from CVE-2025-26465
- 2026-10-03 Alias added: GHSA-jrwv-mv4h-7rrq
- 2026-10-21 Affected versions changed · CNA
- 2026-10-21 Affected versions changed · Red Hat
- 2026-10-21 Affected versions changed · CNA
- 2026-10-22 Affected versions changed · Red Hat
References
Advisory 17
- RHSA-2025:16823
- RHSA-2025:3837
- RHSA-2025:6993
- RHSA-2025:8385
- https://access.redhat.com/security/cve/CVE-2025-26465
- RHBZ#2344780
- https://seclists.org/oss-sec/2025/q1/144
- https://blog.qualys.com/vulnerabilities-threat-research/2025/02/18/qualys-tru-discovers-two-vulnerabilities-in-openssh-cve-2025-26465-cve-2025-26466
- https://lists.debian.org/debian-lts-announce/2025/02/msg00020.html
- https://lists.mindrot.org/pipermail/openssh-unix-announce/2025-February/000161.html
- https://security-tracker.debian.org/tracker/CVE-2025-26465
- https://security.netapp.com/advisory/ntap-20250228-0003/
- https://ubuntu.com/security/CVE-2025-26465
- https://www.openwall.com/lists/oss-security/2025/02/18/1
- https://www.openwall.com/lists/oss-security/2025/02/18/4
- https://www.vicarius.io/vsociety/posts/cve-2025-26465-detect-vulnerable-openssh
- https://www.vicarius.io/vsociety/posts/cve-2025-26465-mitigate-vulnerable-openssh
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Sources
- CVE-2025-26465 · CVE Program
- CVE-2025-26465 · NVD
- FIRST EPSS
- GHSA-jrwv-mv4h-7rrq · GitHub Advisory Database · CC BY 4.0
- CVE-2025-26465 · Red Hat security data · CC BY 4.0
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