Security readout for executives and security teams
Plain-English summary
CVE-2025-26465 can let an attacker impersonate an SSH server when an OpenSSH client has VerifyHostKeyDNS enabled. The impact could expose credentials or session data, but exploitation is constrained by high complexity: sources say the attacker must first exhaust client memory. It is not listed as KEV.
Executive priority
Treat as a moderate-priority infrastructure client update. It is not known exploited in the supplied sources, but it affects trust in SSH server identity and could expose sensitive administrative sessions in the right conditions.
Technical view
OpenSSH mishandles error codes during DNS-based host key verification when VerifyHostKeyDNS is enabled. Under specific memory-exhaustion conditions, this can undermine host key validation and permit a machine-in-the-middle attack. CVSS 3.1 is 6.8 with network attack vector, high complexity, no privileges, user interaction, and high confidentiality and integrity impact.
Likely exposure
Exposure is mainly OpenSSH clients using VerifyHostKeyDNS. The bundle names affected Red Hat openssh packages for RHEL 8, RHEL 9, RHEL 9.4 EUS, Red Hat Discovery 1.14, and Red Hat OpenShift Container Platform 4 rhcos. Other distributions are referenced, but exact affected versions are not fully enumerated here.
Exploitation context
The source bundle does not provide evidence of active exploitation, and KEV is false. Successful attack requires positioning for machine-in-the-middle traffic and first exhausting client memory, making practical exploitation harder. Risk rises where SSH clients rely on DNS host key verification across untrusted networks.
Researcher notes
Focus validation on client-side OpenSSH behavior with VerifyHostKeyDNS enabled. The key constraint is memory exhaustion before host key verification error handling is abused. The source bundle indicates CWE-390 and CVSS AC:H; avoid assuming broad server-side exposure without configuration evidence.
Mitigation direction
- Apply applicable vendor security updates from Red Hat, OpenSSH, Debian, Ubuntu, or platform guidance.
- Inventory SSH clients and configurations that set VerifyHostKeyDNS to yes.
- If VerifyHostKeyDNS is not required, disable it according to approved vendor guidance.
- Prioritize updates for administrator workstations, automation runners, and bastion-adjacent clients.
- Monitor vendor advisories for affected version clarification and backported fixes.
Validation and detection
- Check installed OpenSSH package versions against vendor advisories and errata.
- Review ssh_config, included config files, and user configs for VerifyHostKeyDNS.
- Confirm patched packages are installed on RHEL 8, RHEL 9, and OpenShift nodes where applicable.
- Validate SSH hardening baselines do not depend on vulnerable DNS host key verification behavior.
- Document exceptions where patching or configuration changes are deferred.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-390: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupContainer behavior lookup
The affected technology mentions containers, so container-specific ATT&CK technique review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2025-26465 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N1.65.2redhatVulnerability scoring details
Base CVSS 3.1 score
6.8MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- Source timelineredhat
Reported to Red Hat.
- Source timelineredhat
Made public.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- RHSA-2025:16823CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2025:3837CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2025:6993CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2025:8385CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/security/cve/CVE-2025-26465CVE reference, redhat · vdb-entry, x_refsource_REDHAT
- https://access.redhat.com/solutions/7109879CVE reference, redhat
- RHBZ#2344780CVE reference, redhat · issue-tracking, x_refsource_REDHAT
- https://seclists.org/oss-sec/2025/q1/144CVE reference, redhat
- https://lists.debian.org/debian-lts-announce/2025/02/msg00020.htmlCVE reference, CVE
- https://www.openwall.com/lists/oss-security/2025/02/18/1CVE reference, CVE
- https://www.openwall.com/lists/oss-security/2025/02/18/4CVE reference, CVE
- https://www.theregister.com/2025/02/18/openssh_vulnerabilities_mitm_dos/CVE reference, CVE
- https://bugzilla.suse.com/show_bug.cgi?id=1237040CVE reference, CVE
- https://security-tracker.debian.org/tracker/CVE-2025-26465CVE reference, CVE
- https://ftp.openbsd.org/pub/OpenBSD/patches/7.6/common/008_ssh.patch.sigCVE reference, CVE
- https://ubuntu.com/security/CVE-2025-26465CVE reference, CVE
- https://www.openssh.com/releasenotes.html#9.9p2CVE reference, CVE
- https://blog.qualys.com/vulnerabilities-threat-research/2025/02/18/qualys-tru-discovers-two-vulnerabilities-in-openssh-cve-2025-26465-cve-2025-26466CVE reference, CVE
- https://lists.mindrot.org/pipermail/openssh-unix-announce/2025-February/000161.htmlCVE reference, CVE
- https://security.netapp.com/advisory/ntap-20250228-0003/CVE reference, CVE
- https://www.vicarius.io/vsociety/posts/cve-2025-26465-detect-vulnerable-opensshCVE reference, CVE
- https://www.vicarius.io/vsociety/posts/cve-2025-26465-mitigate-vulnerable-opensshCVE reference, CVE
- https://cert-portal.siemens.com/productcert/html/ssa-082556.htmlCVE reference, siemens-SADP
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Detection of Error Condition Without Action
Detection of Error Condition Without Action represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.