MediumCVE-2025-26465

    Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled (CVE-2025-26465)

    Published Last modified Sources: Siemens ProductCERT, BSI, Ubuntu, Debian LTS, CVE.org, Msrc Update Guide, EUVD, Debian

    What is affected, what to do

    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.

    Update Red Hat Enterprise Linux 8 to version 0:8.0p1-26.el8_10, Red Hat Enterprise Linux 9 to version 0:8.7p1-45.el9, Red Hat Enterprise Linux 9.4 Extended Update Support to version 0:8.7p1-38.el9_4.5.

    Affected
    • OpenSSH lte 6.8p1..9.9p1
    • Red Hat Enterprise Linux 8 lt *..0:8.0p1-26.el8_10
    • Red Hat Enterprise Linux 9 lt *..0:8.7p1-45.el9
    • Red Hat Enterprise Linux 9.4 Extended Update Support lt *..0:8.7p1-38.el9_4.5
    • Red Hat Discovery 1.14 lt *..1.14.3-1748529279
    Fixed in
    • Red Hat Enterprise Linux 8 0:8.0p1-26.el8_10
    • Red Hat Enterprise Linux 9 0:8.7p1-45.el9
    • Red Hat Enterprise Linux 9.4 Extended Update Support 0:8.7p1-38.el9_4.5
    • Red Hat Discovery 1.14 1.14.3-1748529279

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    6.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    6.8

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: Siemens ProductCERT, BSI, Ubuntu, Debian LTS, CVE.org, Msrc Update Guide, EUVD, Debian

    7.7 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 94.6

    Show all metrics
    Severity
    Medium
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    113.50 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    6.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    6.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    7.7 %
    Moderate — model estimates 1-10% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    94.6
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-390

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    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.

    Source: siemens_advisory, BSI CSAF, BSI WID Portal, Ubuntu Security Notices, Debian LTS Advisories, cvelistv5, NVD (NIST), Microsoft Security Update Guide, CVE.org (MITRE), ENISA EUVD, Debian Security Advisories

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    —OpenSSH
    • 6.8p1 – ≤ 9.9p1
    • —
    Red HatRed Hat Discovery 1.14
    • < 1.14.3-1748529279
    • 1.14.3-1748529279
    Red HatRed Hat Enterprise Linux 10
    • —
    • —
    Red HatRed Hat Enterprise Linux 6
    • —
    • —
    Red HatRed Hat Enterprise Linux 7
    • —
    • —
    Red HatRed Hat Enterprise Linux 8
    • < 0:8.0p1-26.el8_10
    • 0:8.0p1-26.el8_10
    Red HatRed Hat Enterprise Linux 9
    • < 0:8.7p1-45.el9
    • 0:8.7p1-45.el9
    Red HatRed Hat Enterprise Linux 9.4 Extended Update Support
    • < 0:8.7p1-38.el9_4.5
    • 0:8.7p1-38.el9_4.5
    Red HatRed Hat OpenShift Container Platform 4
    • —
    • —
    netappactive_iq_unified_manager
    • —
    • —
    netappontap
    • 9
    • —
    openbsdopenssh
    • 6.9 – ≤ 9.8
    • 9.9
    • 6.8
    • —
    • —
    • —
    redhatopenshift_container_platform
    • 4.0
    • —
    Dellintegrated Dell Remote Access Controller
    • < 7.00.00.181
    • < 7.20.30.50
    • 7.00.00.181
    • 7.20.30.50
    DellNetWorker
    • < 19.11.0.6
    • < 19.12.0.2
    • 19.11.0.6
    • 19.12.0.2
    DellPowerProtect Data Domain
    • < 7.13.1.40
    • < 7.10.1.70
    • < 8.3.1.10
    • < 8.4.0.0
    • 7.13.1.40
    • 7.10.1.70
    • 8.3.1.10
    • 8.4.0.0
    DellPowerScale OneFS
    • OneFS
    • —
    DellPowerScale OneFS OneFS
    • < 9.10.1.3
    • < 9.11.0.1
    • 9.10.1.3
    • 9.11.0.1
    DellSecure Connect Gateway
    • < 5.30.0.14
    • 5.30.0.14
    FortinetFortiAnalyzer
    • < 7.2.11
    • < 7.4.7
    • < 7.6.3
    • 7.2.11
    • 7.4.7
    • 7.6.3
    FortinetFortiManager
    • < 7.6.3
    • < 7.4.7
    • < 7.2.11
    • 7.6.3
    • 7.4.7
    • 7.2.11
    HPEHP-UX
    • <Secure Shell A.09.30.010
    • —
    IBMAIX
    • 7.2
    • 7.3
    • —
    • —
    IBMSecurity Verify Access
    • < 11.0.2
    • < 10.0.9.1
    • 11.0.2
    • 10.0.9.1
    IBMVIOS
    • 4.1
    • 3.1
    • —
    • —
    MeinbergLANTIME
    • < 7.08.023
    • 7.08.023
    NetAppData ONTAP
    • 9
    • —
    Open SourceOpenSSH
    • < 9.9p2
    • 9.5p1-9.9p1
    • 6.8p1-9.9p1
    • 9.9p2
    • —
    • —
    OpenBSDOpenBSD
    • 7.5
    • 7.6
    • —
    • —
    QNAPNAS
    • QTS <5.2.4.3079 build 20250321
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebiandebian_linux11.0
    Linuxdebiandebian_linux12.0
    Linuxredhatenterprise_linux9.0
    Linuxdebianopensshbookworm
    Linuxdebianopensshbullseye
    Linuxubuntuopensshfocal
    Linuxubuntuopensshjammy
    Linuxubuntuopensshnoble
    Linuxubuntuopensshoracular

    Weakness classes (CWE)

    • CWE-390Detection of Error Condition Without Action

      Base

      The product detects a specific error, but takes no actions to handle the error.

      Entry at MITRE CWE-390

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2025/26xxx/CVE-2025-26465.json">CVE-2025-26465</a>

      Source identifier: secalert@redhat.com

    2. Record modifiedRed Hat

      Show 20 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2025/26xxx/CVE-2025-26465.json">CVE-2025-26465</a>
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2025:16823
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2025:3837
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2025:6993
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2025:8385
      Referenceadded
      —
      https://access.redhat.com/security/cve/CVE-2025-26465
      Referenceadded
      —
      https://access.redhat.com/solutions/7109879
      Referenceadded
      —
      https://bugzilla.redhat.com/show_bug.cgi?id=2344780
      Referenceadded
      —
      https://seclists.org/oss-sec/2025/q1/144
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2025:16823
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2025:3837
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2025:6993
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2025:8385
      —
      Referenceremoved
      https://access.redhat.com/security/cve/CVE-2025-26465
      —
      Referenceremoved
      https://access.redhat.com/solutions/7109879
      —
      Referenceremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2344780
      —
      Referenceremoved
      https://seclists.org/oss-sec/2025/q1/144
      —
      Reference typeremoved
      https://access.redhat.com/security/cve/CVE-2025-26465 Types: Third Party Advisory
      —
      Reference typeremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2344780 Types: Issue Tracking, Third Party Advisory
      —
      Reference typeremoved
      https://seclists.org/oss-sec/2025/q1/144 Types: Mailing List, Third Party Advisory
      —

      Source identifier: secalert@redhat.com

    3. Record modifiedCISA ADP

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://seclists.org/oss-sec/2025/q1/144
      Referenceremoved
      https://seclists.org/oss-sec/2025/q1/144
      —
      Reference typeremoved
      https://seclists.org/oss-sec/2025/q1/144 Types: Mailing List, Third Party Advisory
      —

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    4. Record modifiedCVE Program

      Show 48 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      http://seclists.org/fulldisclosure/2025/Feb/18
      Referenceadded
      —
      http://seclists.org/fulldisclosure/2025/May/7
      Referenceadded
      —
      http://seclists.org/fulldisclosure/2025/May/8
      Referenceadded
      —
      https://blog.qualys.com/vulnerabilities-threat-research/2025/02/18/qualys-tru-discovers-two-vulnerabilities-in-openssh-cve-2025-26465-cve-2025-26466
      Referenceadded
      —
      https://bugzilla.suse.com/show_bug.cgi?id=1237040
      Referenceadded
      —
      https://ftp.openbsd.org/pub/OpenBSD/patches/7.6/common/008_ssh.patch.sig
      Referenceadded
      —
      https://lists.debian.org/debian-lts-announce/2025/02/msg00020.html
      Referenceadded
      —
      https://lists.mindrot.org/pipermail/openssh-unix-announce/2025-February/000161.html
      Referenceadded
      —
      https://security-tracker.debian.org/tracker/CVE-2025-26465
      Referenceadded
      —
      https://security.netapp.com/advisory/ntap-20250228-0003/
      Referenceadded
      —
      https://ubuntu.com/security/CVE-2025-26465
      Referenceadded
      —
      https://www.openssh.com/releasenotes.html#9.9p2
      Referenceadded
      —
      https://www.openwall.com/lists/oss-security/2025/02/18/1
      Referenceadded
      —
      https://www.openwall.com/lists/oss-security/2025/02/18/4
      Referenceadded
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      https://www.theregister.com/2025/02/18/openssh_vulnerabilities_mitm_dos/
      Referenceadded
      —
      https://www.vicarius.io/vsociety/posts/cve-2025-26465-detect-vulnerable-openssh
      Referenceadded
      —
      https://www.vicarius.io/vsociety/posts/cve-2025-26465-mitigate-vulnerable-openssh
      Referenceremoved
      http://seclists.org/fulldisclosure/2025/Feb/18
      —
      Referenceremoved
      http://seclists.org/fulldisclosure/2025/May/7
      —
      Referenceremoved
      http://seclists.org/fulldisclosure/2025/May/8
      —
      Referenceremoved
      https://blog.qualys.com/vulnerabilities-threat-research/2025/02/18/qualys-tru-discovers-two-vulnerabilities-in-openssh-cve-2025-26465-cve-2025-26466
      —
      Referenceremoved
      https://bugzilla.suse.com/show_bug.cgi?id=1237040
      —
      Referenceremoved
      https://ftp.openbsd.org/pub/OpenBSD/patches/7.6/common/008_ssh.patch.sig
      —
      Referenceremoved
      https://lists.debian.org/debian-lts-announce/2025/02/msg00020.html
      —
      Referenceremoved
      https://lists.mindrot.org/pipermail/openssh-unix-announce/2025-February/000161.html
      —
      Referenceremoved
      https://security-tracker.debian.org/tracker/CVE-2025-26465
      —
      Referenceremoved
      https://security.netapp.com/advisory/ntap-20250228-0003/
      —
      Referenceremoved
      https://ubuntu.com/security/CVE-2025-26465
      —
      Referenceremoved
      https://www.openssh.com/releasenotes.html#9.9p2
      —
      Referenceremoved
      https://www.openwall.com/lists/oss-security/2025/02/18/1
      —
      Referenceremoved
      https://www.openwall.com/lists/oss-security/2025/02/18/4
      —
      Referenceremoved
      https://www.theregister.com/2025/02/18/openssh_vulnerabilities_mitm_dos/
      —
      Referenceremoved
      https://www.vicarius.io/vsociety/posts/cve-2025-26465-detect-vulnerable-openssh
      —
      Referenceremoved
      https://www.vicarius.io/vsociety/posts/cve-2025-26465-mitigate-vulnerable-openssh
      —
      Reference typeremoved
      https://blog.qualys.com/vulnerabilities-threat-research/2025/02/18/qualys-tru-discovers-two-vulnerabilities-in-openssh-cve-2025-26465-cve-2025-26466 Types: Third Party Advisory
      —
      Reference typeremoved
      https://bugzilla.suse.com/show_bug.cgi?id=1237040 Types: Issue Tracking
      —
      Reference typeremoved
      https://ftp.openbsd.org/pub/OpenBSD/patches/7.6/common/008_ssh.patch.sig Types: Patch
      —
      Reference typeremoved
      https://lists.debian.org/debian-lts-announce/2025/02/msg00020.html Types: Third Party Advisory
      —
      Reference typeremoved
      https://lists.mindrot.org/pipermail/openssh-unix-announce/2025-February/000161.html Types: Third Party Advisory
      —
      Reference typeremoved
      https://security-tracker.debian.org/tracker/CVE-2025-26465 Types: Third Party Advisory
      —
      Reference typeremoved
      https://security.netapp.com/advisory/ntap-20250228-0003/ Types: Third Party Advisory
      —
      Reference typeremoved
      https://ubuntu.com/security/CVE-2025-26465 Types: Third Party Advisory
      —
      Reference typeremoved
      https://www.openssh.com/releasenotes.html#9.9p2 Types: Release Notes
      —
      Reference typeremoved
      https://www.openwall.com/lists/oss-security/2025/02/18/1 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      https://www.openwall.com/lists/oss-security/2025/02/18/4 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      https://www.theregister.com/2025/02/18/openssh_vulnerabilities_mitm_dos/ Types: Press/Media Coverage
      —
      Reference typeremoved
      https://www.vicarius.io/vsociety/posts/cve-2025-26465-detect-vulnerable-openssh Types: Third Party Advisory
      —
      Reference typeremoved
      https://www.vicarius.io/vsociety/posts/cve-2025-26465-mitigate-vulnerable-openssh Types: Mitigation, Third Party Advisory
      —

      Source identifier: af854a3a-2127-422b-91ae-364da2661108

    5. Record modifiedSiemens ADP

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-082556.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-585531.html
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-082556.html
      —
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-585531.html
      —

      Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

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