CVE-2025-26465 — Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 7.7% (30-day exploitation probability)+14
- Technical severity (medium)+3
- CISA SSVC: exploitation "poc"+5
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — ftp.openbsd.org (NIST National Vulnerability Database)
- Documented mitigation — www.vicarius.io (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Debian Debian Linux, Netapp Active Iq Unified Manager, Netapp Ontap…).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- Exploitation requires user interaction: tighten email/web filtering and warn affected users.
- EPSS ahead of 95% of scored CVEs: prioritize it in the patch queue.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Debian | Debian Linux | version 11.0version 12.0 | Vulnerable | NIST National Vulnerability Database |
| Netapp | Active Iq Unified Manager | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | Ontap | version 9 | Vulnerable | NIST National Vulnerability Database |
| Openbsd | Openssh | ≥ 6.9 and ≤ 9.8version 6.8-p1version 9.9version 9.9-p1 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux | version 9.0 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Openshift Container Platform | version 4.0 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Red Hat Discovery 1.14 | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Red Hat | Red Hat Enterprise Linux 8 | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Red Hat | Red Hat Enterprise Linux 9 | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Red Hat | Red Hat Enterprise Linux 9.4 Extended Update Support | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Red Hat | Red Hat OpenShift Container Platform 4 | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 6.8 | CVSS 3.1 | Medium | 1.6 | 5.2 | secalert@redhat.com via NIST National Vulnerability Database |
| 6.8 | CVSS 3.1 | Medium | 1.6 | 5.2 | nvd@nist.gov via NIST National Vulnerability Database |
| 6.8 | CVSS 3.1 | Medium | — | — | GitHub, Inc. via GitHub Security Advisories |
| 6.8 | CVSS 3.1 | Medium | — | — | redhat via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 21, 2026 → Oct 22, 2026 · 2 reading(s) · max 7.72%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · red hat/red hat openshift container platform 4
- Affected products added · red hat/red hat enterprise linux 8, red hat/red hat enterprise linux 9, red hat/red hat enterprise linux 9.4 extended up
- SSVC assessment updated
- Record published
- Fix documented
- Affected products added · openbsd/openssh, netapp/active iq unified manager, netapp/ontap, redhat/openshift container platform, debian/debian linu
- CVSS changed · 6.8
- Source status changed · → Modified
- Record created in this database
- 2025
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 21, 2026 – Oct 21, 2026
- 1× Official description updated · Oct 21, 2026 – Oct 21, 2026
References
30 on the record
- ftp.openbsd.org/pub/OpenBSD/patches/7.6/common/008_ssh.patch.sig
- www.vicarius.io/vsociety/posts/cve-2025-26465-mitigate-vulnerable-openssh
- blog.qualys.com/vulnerabilities-threat-research/2025/02/18/qualys-tru-discovers-two-v
- www.openwall.com/lists/oss-security/2025/02/18/4
- access.redhat.com/errata/RHSA-2025:16823
- bugzilla.suse.com/show_bug.cgi
- bugzilla.redhat.com/show_bug.cgi
- github.com/advisories/GHSA-jrwv-mv4h-7rrq
- www.theregister.com/2025/02/18/openssh_vulnerabilities_mitm_dos/
- access.redhat.com/errata/RHSA-2025:3837
- seclists.org/fulldisclosure/2025/May/8
- nvd.nist.gov/vuln/detail/CVE-2025-26465
- www.openwall.com/lists/oss-security/2025/02/18/1
- seclists.org/fulldisclosure/2025/May/7
- access.redhat.com/security/cve/CVE-2025-26465
- seclists.org/oss-sec/2025/q1/144
- lists.debian.org/debian-lts-announce/2025/02/msg00020.html
- access.redhat.com/errata/RHSA-2025:8385
- lists.mindrot.org/pipermail/openssh-unix-announce/2025-February/000161.html
- access.redhat.com/solutions/7109879
- cert-portal.siemens.com/productcert/html/ssa-082556.html
- cert-portal.siemens.com/productcert/html/ssa-585531.html
- www.openssh.com/releasenotes.html
- security.netapp.com/advisory/ntap-20250228-0003/
- access.redhat.com/errata/RHSA-2025:6993
- www.vicarius.io/vsociety/posts/cve-2025-26465-detect-vulnerable-openssh
- seclists.org/fulldisclosure/2025/Feb/18
- ubuntu.com/security/CVE-2025-26465
- www.theregister.com/2025/02/18/openssh_vulnerabilities_mitm_dos
- security-tracker.debian.org/tracker/CVE-2025-26465
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-115484 Open-iscsi: open-iscsi: dhcpv4 option parser heap out-of-bounds read in iscsiuio parse_msg 17h
- High CVE-2026-115486 Open-iscsi: open-iscsi: ipv6 neighbor discovery missing option length validation in iscsiuio allows arp table poisoning 17h
- Medium CVE-2026-115485 Open-iscsi: open-iscsi: dhcpv6 vendor option strlen heap out-of-bounds read and 1-byte write in iscsiuio 17h
- Medium CVE-2026-115424 Oc: oc: symlink/hardlink target validation bypass in oc image extract allows file write outside destination 20h
- Low CVE-2026-115449 Libslirp: libslirp: icmp echo reply length desynchronization leaks host ip to guest 20h
- Medium CVE-2026-115221 Ipa: freeipa: freeipa uses subject cn as proof of certificate ownership 20h
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2025-26465 is "Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled", rated Medium. It affects Debian Linux (Debian); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.8 describes technical severity. EPSS 7.72% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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