HighCVE-2026-84243

    glibc: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (CVE-2026-84243)

    Published Sources: BSI

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    What is affected, what to do

    The gettext family of functions in the GNU C Library version 2.0 and later accept LANGUAGE environment variable entries that contain '/' or that are equal to "..", unless the program is setuid or setgid (AT_SECURE). An attacker who can set LANGUAGE in the environment of a program that uses gettext can make it load a message catalog (.mo file) from an arbitrary location in the file system.

    The available sources name no fixed version. Check the vendor guidance in the references below.

    Affected
    • The GNU C Library Glibc gte 2.0..*

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

    Metrics

    7.0

    Priority

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

    Source: Vendor (CNA), CVSS v3

    7.0

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: BSI

    0.3 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 22.6

    Show all metrics
    Severity
    High
    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
    69.07 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
    7.0 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
    7.0
    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
    0.3 %
    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
    22.6
    Elevated — this CVE ranks above at least 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: total
    Source: CISA Vulnrichment, as of 30 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
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    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 gettext family of functions in the GNU C Library version 2.0 and later accept LANGUAGE environment variable entries that contain '/' or that are equal to "..", unless the program is setuid or setgid (AT_SECURE). An attacker who can set LANGUAGE in the environment of a program that uses gettext can make it load a message catalog (.mo file) from an arbitrary location in the file system. A crafted .mo file can crash the program through out-of-range offsets, or supply translations whose format directives do not match the arguments passed by the program. That causes undefined behaviour in the printf family of functions and may allow arbitrary code execution with the privileges of the program. The safety of message catalogs relies on them being installed in trusted, read-only locations, and the directory traversal bypasses this. The fix for CVE-2014-0475 rejects ".." path components in locale names passed to setlocale or taken from the LC_ALL, LC_* and LANG environment variables. gettext reads LANGUAGE directly and appends each colon-separated entry to the message catalog directory, so that fix did not cover LANGUAGE. LANGUAGE is only used when the LC_MESSAGES locale is not "C", "C.<encoding>" or "POSIX", so the attacker must also be able to select another installed locale, for example through LANG or LC_ALL. Exploitation also requires that the attacker can place the crafted file in a location readable by the target program, and that the environment crosses a trust boundary without the program running as AT_SECURE. An example is an SSH server that accepts LANGUAGE and LANG from clients through the AcceptEnv directive and restricts an account to a forced command; the attacker may use this to escape the restriction.

    Source: BSI WID Portal

    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
    The GNU C Libraryglibc
    • ≥ 2.0
    • —

    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

    • inbox.sourceware.orglibc-alpha/20261012112453.47383-1-avinal.xlvii@gmail.comMailing list, Patch
    • sourceware.orgbugzilla/show_bug.cgi?id=17142Issue tracking
    • sourceware.orggit/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0025Vendor advisory

    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 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentremoved
      {"id":"CVE-2026-84243","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-30T20:02:43.517842Z"}
      —
      SSVC assessmentadded
      —
      {"id":"CVE-2026-84243","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-30T00:00:00+00:00"}

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

    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-2026-84243","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-30T20:02:43.517842Z"}

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

    3. Received3ff69d7a…

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

      Weakness type: CWE-22

      Description added or changed

      Show 7 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      The gettext family of functions in the GNU C Library version 2.0 and later accept LANGUAGE environment variable entries that contain '/' or that are equal to "..", unless the program is setuid or setgid (AT_SECURE). An attacker who can set LANGUAGE in the environment of a program that uses gettext can make it load a message catalog (.mo file) from an arbitrary location in the file system. A crafted .mo file can crash the program through out-of-range offsets, or supply translations whose format directives do not match the arguments passed by the program. That causes undefined behaviour in the printf family of functions and may allow arbitrary code execution with the privileges of the program. The safety of message catalogs relies on them being installed in trusted, read-only locations, and the directory traversal bypasses this. The fix for CVE-2014-0475 rejects ".." path components in locale names passed to setlocale or taken from the LC_ALL, LC_* and LANG environment variables. gettext reads LANGUAGE directly and appends each colon-separated entry to the message catalog directory, so that fix did not cover LANGUAGE. LANGUAGE is only used when the LC_MESSAGES locale is not "C", "C.<encoding>" or "POSIX", so the attacker must also be able to select another installed locale, for example through LANG or LC_ALL. Exploitation also requires that the attacker can place the crafted file in a location readable by the target program, and that the environment crosses a trust boundary without the program running as AT_SECURE. An example is an SSH server that accepts LANGUAGE and LANG from clients through the AcceptEnv directive and restricts an account to a forced command; the attacker may use this to escape the restriction.
      CVSSadded
      —
      AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
      Weakness type (CWE)added
      —
      CWE-22
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/84xxx/CVE-2026-84243.json">CVE-2026-84243</a>
      Referenceadded
      —
      https://inbox.sourceware.org/libc-alpha/20261012112453.47383-1-avinal.xlvii@gmail.com
      Referenceadded
      —
      https://sourceware.org/bugzilla/show_bug.cgi?id=17142
      Referenceadded
      —
      https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0025

      Source identifier: 3ff69d7a-14f2-4f67-a097-88dee7810d18

    Linked CVEs

    Linked CVEs
    HighCVE-2026-84243gettext: Directory traversal via the LANGUAGE environment variable7.0—
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