MediumCVE-2026-104871

    Angular SSR: Path Traversal to Sibling Directories in CommonEngine on Windows (CVE-2026-104871)

    Published Last modified Sources: BSI, OSV, CVE.org, Hersteller

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    What is affected, what to do

    The Angular SSR is a server-rise rendering tool for Angular applications. Prior to versions 20.3.36, 21.2.23, and 22.1.7, the CommonEngine retrieveSSGPage prerendered-page retrieval logic in @angular/ssr/node, and in @angular/ssr for versions 17 through 18, accepts a relative request URL containing a backslash parent-traversal segment on Windows.

    Update Angular-cli to version 20.3.36.

    Affected
    • Angular-cli gte 21.0.0, < 21.2.23..*
    • Angular-cli lt *..20.3.36
    Fixed in
    • Angular-cli 20.3.36

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

    Metrics

    6.3

    Priority

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

    Source: Vendor (CNA), CVSS v4

    6.3

    CVSS v4

    Severity Medium on the scale from 0 to 10.

    Source: BSI, OSV, CVE.org, Hersteller

    0.4 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 36.6

    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
    71.26 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
    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
    6.3 Methodology
    CVSS v4

    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
    6.3
    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
    0.4 %
    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
    36.6
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    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 2 October 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-22

    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

    The Angular SSR is a server-rise rendering tool for Angular applications. Prior to versions 20.3.36, 21.2.23, and 22.1.7, the CommonEngine retrieveSSGPage prerendered-page retrieval logic in @angular/ssr/node, and in @angular/ssr for versions 17 through 18, accepts a relative request URL containing a backslash parent-traversal segment on Windows. The non-special resolve:// URL base preserves the backslash, path.join interprets it as a Windows separator, and the pagePath.startsWith(normalize(publicPath)) check incorrectly accepts a sibling output directory whose name shares the configured public-directory prefix. An unauthenticated requester can therefore retrieve a sibling prerendered HTML page when that page contains the Angular SSG marker. The issue is limited to Windows deployments that pass relative request URLs to CommonEngine.render, have a prefix-sharing sibling output directory, and contain qualifying prerendered Angular HTML; it does not provide arbitrary file read. This issue is fixed in versions 20.3.36, 21.2.23, and 22.1.7.

    Source: BSI CSAF, BSI WID Portal, OSV (Open Source Vulnerabilities), cvelistv5, NVD (NIST), GitHub 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
    angularangular-cli
    • ≥ 21.0.0, < 21.2.23
    • < 20.3.36
    • —
    • 20.3.36
    Open SourceAngular
    • < 20.3.36
    • < 21.2.23
    • < 22.1.7
    • 20.3.36
    • 21.2.23
    • 22.1.7

    Vendors and products

    Weakness classes (CWE)

    • CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

      Base

      The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

      Entry at MITRE CWE-22

    References & sources

    • github.comangular/angular-cli/security/advisories/GHSA-7g7c-h8rr-7p6qx_refsource_CONFIRM
    • github.comangular/angular-cli/commit/645e41a47d21b7651837a4250de99af05096…x_refsource_MISC
    • github.comangular/angular-cli/commit/70748ca8e76fe4b42798719410336119d943…x_refsource_MISC
    • github.comangular/angular-cli/commit/bb72145f9ab45aee29f523236b3a25cd0813…x_refsource_MISC
    • github.comangular/angular-cli/commit/c3e5982e49705f0f6a913cb94622b4c555d2…x_refsource_MISC
    • github.comangular/angular-cli/releases/tag/v20.3.36x_refsource_MISC
    • github.comangular/angular-cli/releases/tag/v21.2.23x_refsource_MISC
    • github.comangular/angular-cli/releases/tag/v22.1.7x_refsource_MISC
    • NVD (NIST)vuln/detail/CVE-2026-104871advisory
    • github.comangular/angular-clipackage

    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 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-2026-104871","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-02T20:12:27.563771Z"}

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

    2. ReceivedGitHub

      CVSS V4.0: AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

      Weakness type: CWE-22

      Description added or changed

      Show 12 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      The Angular SSR is a server-rise rendering tool for Angular applications. Prior to versions 20.3.36, 21.2.23, and 22.1.7, the CommonEngine retrieveSSGPage prerendered-page retrieval logic in @angular/ssr/node, and in @angular/ssr for versions 17 through 18, accepts a relative request URL containing a backslash parent-traversal segment on Windows. The non-special resolve:// URL base preserves the backslash, path.join interprets it as a Windows separator, and the pagePath.startsWith(normalize(publicPath)) check incorrectly accepts a sibling output directory whose name shares the configured public-directory prefix. An unauthenticated requester can therefore retrieve a sibling prerendered HTML page when that page contains the Angular SSG marker. The issue is limited to Windows deployments that pass relative request URLs to CommonEngine.render, have a prefix-sharing sibling output directory, and contain qualifying prerendered Angular HTML; it does not provide arbitrary file read. This issue is fixed in versions 20.3.36, 21.2.23, and 22.1.7.
      CVSSadded
      —
      AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
      Weakness type (CWE)added
      —
      CWE-22
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/104xxx/CVE-2026-104871.json">CVE-2026-104871</a>
      Referenceadded
      —
      https://github.com/angular/angular-cli/commit/645e41a47d21b7651837a4250de99af0509626e2
      Referenceadded
      —
      https://github.com/angular/angular-cli/commit/70748ca8e76fe4b42798719410336119d943e755
      Referenceadded
      —
      https://github.com/angular/angular-cli/commit/bb72145f9ab45aee29f523236b3a25cd0813a841
      Referenceadded
      —
      https://github.com/angular/angular-cli/commit/c3e5982e49705f0f6a913cb94622b4c555d2d914
      Referenceadded
      —
      https://github.com/angular/angular-cli/releases/tag/v20.3.36
      Referenceadded
      —
      https://github.com/angular/angular-cli/releases/tag/v21.2.23
      Referenceadded
      —
      https://github.com/angular/angular-cli/releases/tag/v22.1.7
      Referenceadded
      —
      https://github.com/angular/angular-cli/security/advisories/GHSA-7g7c-h8rr-7p6q

      Source identifier: security-advisories@github.com

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