MediumCVE-2026-91769

    TLS Hostname Verification Falls Back to CN After SAN Mismatch (CVE-2026-91769)

    Published Last modified Sources: SUSE, Red Hat, Debian LTS, Ubuntu, Debian, BSI, OSV, Msrc Update Guide, CVE.org

    What is affected, what to do

    PHP's OpenSSL stream peer verification checks the certificate's subjectAltName entries first and, whenever no entry matches, falls back to the Common Name. RFC 6125 requires the CN to be ignored once the certificate presents any service identity, so a certificate carrying a non-matching DNS SAN was still accepted when its CN matched the requested peer_name.

    An exploit is publicly available. Update PHP to version 8.2.34, PHP to version 8.3.35, PHP to version 8.4.26.

    Affected
    • PHP lt 8.2.0..8.2.34
    • PHP lt 8.3.0..8.3.35
    • PHP lt 8.4.0..8.4.26
    • PHP lt 8.5.0..8.5.11
    Fixed in
    • PHP 8.2.34
    • PHP 8.3.35
    • PHP 8.4.26
    • PHP 8.5.11

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

    Metrics

    4.3

    Priority

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

    Source: Vendor (CNA), CVSS v3

    4.3

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: SUSE, Red Hat, Debian LTS, Ubuntu, Debian, BSI, OSV, Msrc Update Guide, CVE.org

    0.2 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 5.0

    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
    51.26 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
    PoC (publicly reported)
    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
    4.3 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
    4.3
    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
    0.2 %
    Low — model estimates < 1% 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
    5.0
    Low — this CVE sits in the lower 10% of all CVEs scored today.
    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
    CISA assessment (SSVC)
    Exploitation: none known · not automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 28 September 2026
    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-297

    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

    PHP's OpenSSL stream peer verification checks the certificate's subjectAltName entries first and, whenever no entry matches, falls back to the Common Name. RFC 6125 requires the CN to be ignored once the certificate presents any service identity, so a certificate carrying a non-matching DNS SAN was still accepted when its CN matched the requested peer_name. A certificate trusted by the client for one name can therefore be used to impersonate another.

    Source: suse_csaf, redhat_csaf, Debian LTS Advisories, Ubuntu Security Notices, Debian Security Advisories, BSI WID Portal, BSI CSAF, OSV (Open Source Vulnerabilities), Microsoft Security Update Guide, NVD (NIST), cvelistv5, CVE.org (MITRE)

    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
    PHP GroupPHP
    • 8.4.0 – < 8.4.26
    • 8.3.0 – < 8.3.35
    • 8.2.0 – < 8.2.34
    • 8.5.0 – < 8.5.11
    • 8.4.26
    • 8.3.35
    • 8.2.34
    • 8.5.11
    phpphp
    • 8.2.0 – < 8.2.34
    • 8.4.0 – < 8.4.26
    • 8.3.0 – < 8.3.35
    • 8.5.0 – < 8.5.11
    • 8.2.34
    • 8.4.26
    • 8.3.35
    • 8.5.11
    Open SourcePHP
    • < 8.5.11
    • < 8.2.34
    • < 8.3.35
    • < 8.4.26
    • 8.5.11
    • 8.2.34
    • 8.3.35
    • 8.4.26
    Distribution and container packages (12)

    Downstream packages (e.g. Bitnami, Debian, Ubuntu, Red Hat). Versions refer to the distribution, not the vendor.

    Distribution and container packages
    Affected versionsFixed in
    bitnamilibphp
    • 8.3.0
    • 8.5.0
    • 8.2.0
    • 8.4.0
    • 8.3.35
    • 8.5.11
    • 8.2.34
    • 8.4.26
    bitnamiphp
    • 8.5.0
    • 8.4.0
    • 8.2.0
    • 8.3.0
    • 8.5.11
    • 8.4.26
    • 8.2.34
    • 8.3.35
    bitnamiphp-min
    • 8.2.0
    • 8.4.0
    • 8.5.0
    • 8.3.0
    • 8.2.34
    • 8.4.26
    • 8.5.11
    • 8.3.35

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxubuntuphp5trusty
    Linuxubuntuphp7.0xenial
    Linuxubuntuphp7.2bionic
    Linuxubuntuphp7.4focal
    Linuxubuntuphp8.1jammy
    Linuxdebianphp8.2bookworm
    Linuxubuntuphp8.3noble
    Linuxdebianphp8.4trixie
    Linuxubuntuphp8.5resolute
    Linuxubuntuphp8.5stonking

    Weakness classes (CWE)

    • CWE-297Improper Validation of Certificate with Host Mismatch

      Variant

      The product communicates with a host that provides a certificate, but the product does not properly ensure that the certificate is actually associated with that host.

      Entry at MITRE CWE-297

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    Reference tagged as exploitgithub.com (opens in a new tab)PoC (publicly reported)reported, not verified—

    References & sources

    • github.comphp/php-src/security/advisories/GHSA-vvx9-73fr-5jjxVendor advisory, Vendor advisory, Exploit, advisory
    • NVD (NIST)vuln/detail/CVE-2026-91769web

    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. Initial analysis by NVDNVD

      Newly listed as affected:
      • PHP (8.2.0 – before 8.2.34; 8.3.0 – before 8.3.35; 8.4.0 – before 8.4.26; 8.5.0 – before 8.5.11)
      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      OR *cpe:2.3:a:php:php:*:*:*:*:*:*:*:* versions from (including) 8.2.0 up to (excluding) 8.2.34 *cpe:2.3:a:php:php:*:*:*:*:*:*:*:* versions from (including) 8.3.0 up to (excluding) 8.3.35 *cpe:2.3:a:php:php:*:*:*:*:*:*:*:* versions from (including) 8.4.0 up to (excluding) 8.4.26 *cpe:2.3:a:php:php:*:*:*:*:*:*:*:* versions from (including) 8.5.0 up to (excluding) 8.5.11
      Reference typeadded
      —
      PHP Group: https://github.com/php/php-src/security/advisories/GHSA-vvx9-73fr-5jjx Types: Exploit, Vendor Advisory

      Source identifier: nvd@nist.gov

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-91769","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-09-28T12:56:47.310384Z"}

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

    3. ReceivedPHP

      CVSS V3.1: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

      Weakness type: CWE-297

      Description added or changed

      Show 5 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      PHP's OpenSSL stream peer verification checks the certificate's subjectAltName entries first and, whenever no entry matches, falls back to the Common Name. RFC 6125 requires the CN to be ignored once the certificate presents any service identity, so a certificate carrying a non-matching DNS SAN was still accepted when its CN matched the requested peer_name. A certificate trusted by the client for one name can therefore be used to impersonate another.
      CVSSadded
      —
      AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
      Weakness type (CWE)added
      —
      CWE-297
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/91xxx/CVE-2026-91769.json">CVE-2026-91769</a>
      Referenceadded
      —
      https://github.com/php/php-src/security/advisories/GHSA-vvx9-73fr-5jjx

      Source identifier: security@php.net

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