Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled

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Summary

CVECVE-2025-26465
StatePUBLISHED
Assignerredhat
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-02-18 19:15:29 UTC
Updated2026-05-12 13:16:40 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 6.8 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Problem Types: CWE-390 | CWE-390 Detection of Error Condition Without Action

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
3.1[email protected]Secondary6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
3.1CNACVSS6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Debian Debian Linux 11.0 All All All
Operating System Debian Debian Linux 12.0 All All All
Application Netapp Active Iq Unified Manager - All All All
Application Netapp Ontap 9 All All All
Application Openbsd Openssh 6.8 p1 All All
Application Openbsd Openssh 9.9 - All All
Application Openbsd Openssh 9.9 p1 All All
Application Openbsd Openssh All All All All
Operating System Redhat Enterprise Linux 9.0 All All All
Application Redhat Openshift Container Platform 4.0 All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Red Hat Red Hat Enterprise Linux 8 unaffected 0:8.0p1-26.el8_10 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 8 unaffected 0:8.0p1-26.el8_10 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 9 unaffected 0:8.7p1-45.el9 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 9 unaffected 0:8.7p1-45.el9 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 9.4 Extended Update Support unaffected 0:8.7p1-38.el9_4.5 * rpm Not specified
CNA Red Hat Red Hat Discovery 1.14 unaffected sha256:f33991d766b618a128fb99fbe4f9b61c5004f7c6aa73b2b38e28d59e56c64d63 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 10 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 6 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 7 Not specified Not specified
CNA Red Hat Red Hat OpenShift Container Platform 4 Not specified Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified

References

ReferenceSourceLinkTags
www.openwall.com/lists/oss-security/2025/02/18/1 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com Mailing List, Third Party Advisory
www.theregister.com/2025/02/18/openssh_vulnerabilities_mitm_dos af854a3a-2127-422b-91ae-364da2661108 www.theregister.com Press/Media Coverage
bugzilla.suse.com/show_bug.cgi af854a3a-2127-422b-91ae-364da2661108 bugzilla.suse.com Issue Tracking
ubuntu.com/security/CVE-2025-26465 af854a3a-2127-422b-91ae-364da2661108 ubuntu.com Third Party Advisory
seclists.org/fulldisclosure/2025/May/7 af854a3a-2127-422b-91ae-364da2661108 seclists.org
ftp.openbsd.org/pub/OpenBSD/patches/7.6/common/008_ssh.patch.sig af854a3a-2127-422b-91ae-364da2661108 ftp.openbsd.org Patch
access.redhat.com/security/cve/CVE-2025-26465 [email protected] access.redhat.com Third Party Advisory
access.redhat.com/errata/RHSA-2025:6993 [email protected] access.redhat.com
www.vicarius.io/vsociety/posts/cve-2025-26465-mitigate-vulnerable-openssh af854a3a-2127-422b-91ae-364da2661108 www.vicarius.io Mitigation, Third Party Advisory
cert-portal.siemens.com/productcert/html/ssa-082556.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
access.redhat.com/solutions/7109879 [email protected] access.redhat.com
security.netapp.com/advisory/ntap-20250228-0003 af854a3a-2127-422b-91ae-364da2661108 security.netapp.com Third Party Advisory
blog.qualys.com/vulnerabilities-threat-research/2025/02/18/qualys-tru-discove... af854a3a-2127-422b-91ae-364da2661108 blog.qualys.com Third Party Advisory
www.openwall.com/lists/oss-security/2025/02/18/4 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com Mailing List, Third Party Advisory
bugzilla.redhat.com/show_bug.cgi [email protected] bugzilla.redhat.com Issue Tracking, Third Party Advisory
lists.debian.org/debian-lts-announce/2025/02/msg00020.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Third Party Advisory
www.vicarius.io/vsociety/posts/cve-2025-26465-detect-vulnerable-openssh af854a3a-2127-422b-91ae-364da2661108 www.vicarius.io Third Party Advisory
seclists.org/fulldisclosure/2025/May/8 af854a3a-2127-422b-91ae-364da2661108 seclists.org
www.openssh.com/releasenotes.html af854a3a-2127-422b-91ae-364da2661108 www.openssh.com Release Notes
lists.mindrot.org/pipermail/openssh-unix-announce/2025-February/000161.html af854a3a-2127-422b-91ae-364da2661108 lists.mindrot.org Third Party Advisory
security-tracker.debian.org/tracker/CVE-2025-26465 af854a3a-2127-422b-91ae-364da2661108 security-tracker.debian.org Third Party Advisory
access.redhat.com/errata/RHSA-2025:3837 [email protected] access.redhat.com
access.redhat.com/errata/RHSA-2025:16823 [email protected] access.redhat.com
seclists.org/fulldisclosure/2025/Feb/18 af854a3a-2127-422b-91ae-364da2661108 seclists.org
access.redhat.com/errata/RHSA-2025:8385 [email protected] access.redhat.com
seclists.org/oss-sec/2025/q1/144 134c704f-9b21-4f2e-91b3-4a467353bcc0 seclists.org Mailing List, Third Party Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

SourceTimeEvent
CNA2025-02-10T21:56:03.853ZReported to Red Hat.
CNA2025-02-17T00:00:00.000ZMade public.

Workarounds

CNA: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

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