Medium
Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled
Type: advisorySources: OSV
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2025-26465
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 7 Nov 2026, 04:25 UTC · Revision 1
Source evidence
Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled
core-osv · Original sourcePublished 18 Feb 2025, 18:27 UTC
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.
osv:CVE-2025-26465
Complete source record
{
"id": "a0287f0dad3b7decd60826caeff9fe4e7770bf23ce0dc15245d62904b68691cb",
"url": "https://osv.dev/vulnerability/CVE-2025-26465",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled",
"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.",
"evidence": "osv:CVE-2025-26465",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2025-26465",
"aliases": [
"CVE-2025-26465"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/openssh/openssh-portable",
"type": "GIT",
"events": [
{
"introduced": "7de4b03a6e4071d454b72927ffaf52949fa34545"
},
{
"last_affected": "6849957945754e6551e515f41e8cf3937cda222d"
},
{
"introduced": "9f82e5a9042f2d872e98f48a876fcab3e25dd9bb"
},
{
"last_affected": "53a80baaebda180f46e6e8571f3ff800e1f5c496"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:openbsd:openssh:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "6.9"
},
{
"last_affected": "9.8"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:openbsd:openssh:6.8:p1:*:*:*:*:*:*",
"range": [
{
"introduced": "6.8-p1"
},
{
"last_affected": "6.8-p1"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:openbsd:openssh:9.9:p1:*:*:*:*:*:*",
"range": [
{
"introduced": "9.9-p1"
},
{
"last_affected": "9.9-p1"
}
],
"source": "CPE_STRING"
}
]
}
}
],
"versions": [
"6.8-p1",
"9.9-p1",
"V_9_5_P1",
"V_9_2_P1",
"V_9_9_P1",
"V_9_8_P1",
"V_9_7_P1",
"V_9_6_P1",
"V_9_3_P1",
"V_9_1_P1",
"V_9_0_P1",
"V_8_9_P1",
"V_8_8_P1",
"V_8_7_P1",
"V_8_6_P1",
"V_8_5_P1",
"V_8_4_P1",
"V_8_2_P1",
"V_8_1_P1",
"V_8_0_P1",
"V_7_9_P1",
"V_7_8_P1",
"V_7_7_P1",
"V_7_6_P1",
"V_7_5_P1",
"V_7_4_P1",
"V_7_3_P1",
"V_7_2_P1",
"V_7_1_P1",
"V_7_0_P1",
"V_6_9_P1"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-26465.json"
}
}
],
"modified": "2026-10-28T02:30:49.646440524Z",
"provider": "osv",
"references": [
"https://access.redhat.com/downloads/content/package-browser/",
"https://access.redhat.com/solutions/7109879",
"https://catalog.redhat.com/software/containers/",
"https://cert-portal.siemens.com/productcert/html/ssa-082556.html",
"https://cert-portal.siemens.com/productcert/html/ssa-585531.html",
"https://ftp.openbsd.org/pub/OpenBSD/patches/7.6/common/008_ssh.patch.sig",
"https://lists.debian.org/debian-lts-announce/2025/02/msg00020.html",
"https://lists.mindrot.org/pipermail/openssh-unix-announce/2025-February/000161.html",
"https://seclists.org/oss-sec/2025/q1/144",
"https://security-tracker.debian.org/tracker/CVE-2025-26465",
"https://ubuntu.com/security/CVE-2025-26465",
"https://www.openssh.com/",
"https://www.openssh.com/releasenotes.html#9.9p2",
"https://www.openwall.com/lists/oss-security/2025/02/18/1",
"https://www.openwall.com/lists/oss-security/2025/02/18/4",
"https://www.theregister.com/2025/02/18/openssh_vulnerabilities_mitm_dos/",
"https://www.vicarius.io/vsociety/posts/cve-2025-26465-detect-vulnerable-openssh",
"https://www.vicarius.io/vsociety/posts/cve-2025-26465-mitigate-vulnerable-openssh",
"https://access.redhat.com/errata/RHSA-2025:16823",
"https://access.redhat.com/errata/RHSA-2025:3837",
"https://access.redhat.com/errata/RHSA-2025:6993",
"https://access.redhat.com/errata/RHSA-2025:8385",
"https://access.redhat.com/security/cve/CVE-2025-26465",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/26xxx/CVE-2025-26465.json",
"https://nvd.nist.gov/vuln/detail/CVE-2025-26465",
"https://security.netapp.com/advisory/ntap-20250228-0003/",
"https://bugzilla.redhat.com/show_bug.cgi?id=2344780",
"https://bugzilla.suse.com/show_bug.cgi?id=1237040",
"https://anongit.mindrot.org/openssh.git",
"https://blog.qualys.com/vulnerabilities-threat-research/2025/02/18/qualys-tru-discovers-two-vulnerabilities-in-openssh-cve-2025-26465-cve-2025-26466"
],
"provider_metadata": {
"cwe_ids": [
"CWE-390"
],
"cna_assigner": "redhat",
"unresolved_ranges": [
{
"extracted_events": [
{
"range": [
{
"fixed": "0:8.0p1-26.el8_10"
},
{
"fixed": "0:8.0p1-26.el8_10"
},
{
"fixed": "0:8.7p1-45.el9"
},
{
"fixed": "0:8.7p1-45.el9"
},
{
"fixed": "0:8.7p1-38.el9_4.5"
},
{
"fixed": "1.14.3-1748529279"
}
],
"source": "AFFECTED_FIELD",
"strategy": "InverseAffectedRanges"
}
]
},
{
"extracted_events": [
{
"range": [
{
"introduced": "6.8p1"
},
{
"last_affected": "9.9p1"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/26xxx/CVE-2025-26465.json"
}
},
"related_cves": [
{
"value": "CVE-2025-26465",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 518118,
"published_at": "2025-02-18T18:27:16.843+00:00"
}