CriticalCVE-2026-28808

    ScriptAlias CGI targets bypass directory auth in inets httpd (mod_auth vs mod_cgi path mismatch) (CVE-2026-28808)

    Published Last modified Sources: Debian, CVE.org, Msrc Update Guide, OSV, EUVD, BSI

    What is affected, what to do

    Incorrect Authorization vulnerability in Erlang OTP (inets modules) allows unauthenticated access to CGI scripts protected by directory rules when served via script_alias. When script_alias maps a URL prefix to a directory outside DocumentRoot, mod_auth evaluates directory-based access controls against the DocumentRoot-relative path while mod_cgi executes the script at the ScriptAlias-resolved path.

    Update erlang\/inets to version 9.1.0.6, erlang\/otp to version 28.4.2, Erlang/OTP to version 27.3.4.10.

    Affected
    • Erlang OTP gte 17.0..*
    • Erlang OTP gte 5.10..*

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

    Metrics

    9.8

    Priority

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

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: Debian, CVE.org, Msrc Update Guide, OSV, EUVD, BSI

    0.6 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 46.3

    Show all metrics
    Severity
    Critical
    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
    82.09 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
    9.8 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
    9.8
    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
    8.3
    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
    0.6 %
    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
    46.3
    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 · automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 7 April 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-863, CWE-551

    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

    Incorrect Authorization vulnerability in Erlang OTP (inets modules) allows unauthenticated access to CGI scripts protected by directory rules when served via script_alias. When script_alias maps a URL prefix to a directory outside DocumentRoot, mod_auth evaluates directory-based access controls against the DocumentRoot-relative path while mod_cgi executes the script at the ScriptAlias-resolved path. This path mismatch allows unauthenticated access to CGI scripts that directory rules were meant to protect. This vulnerability is associated with program files lib/inets/src/http_server/mod_alias.erl, lib/inets/src/http_server/mod_auth.erl, and lib/inets/src/http_server/mod_cgi.erl. This issue affects OTP from OTP 17.0 before OTP 26.2.5.19, OTP 27.3.4.10, and OTP 28.4.2, corresponding to inets from 5.10 before 9.1.0.6, 9.3.2.4, and 9.6.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.

    Source: Debian Security Advisories, NVD (NIST), Microsoft Security Update Guide, cvelistv5, OSV (Open Source Vulnerabilities), CVE.org (MITRE), ENISA EUVD, BSI WID Portal, BSI CSAF

    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
    ErlangOTP
    • ≥ 5.10
    • ≥ 17.0
    • —
    • —
    erlangerlang\/inets
    • 5.10 – < 9.1.0.6
    • 9.2 – < 9.3.2.4
    • 9.4 – < 9.6.2
    • 9.1.0.6
    • 9.3.2.4
    • 9.6.2
    erlangerlang\/otp
    • 28.0 – < 28.4.2
    • 27.0 – < 27.3.4.10
    • 17.0 – < 26.2.5.19
    • 28.4.2
    • 27.3.4.10
    • 26.2.5.19
    MicrosoftAzure Linux
    • azl3
    • —
    Open SourceErlang/OTP
    • < 27.3.4.10
    • < 26.2.5.19
    • < 28.4.2
    • 27.3.4.10
    • 26.2.5.19
    • 28.4.2
    Open SourceErlang/OTP inets
    • < 9.6.2
    • < 9.1.0.6
    • < 9.3.2.4
    • 9.6.2
    • 9.1.0.6
    • 9.3.2.4

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianerlangtrixie

    Weakness classes (CWE)

    • CWE-863Incorrect Authorization

      Class

      The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

      Entry at MITRE CWE-863

    • CWE-551Incorrect Behavior Order: Authorization Before Parsing and Canonicalization

      Base

      If a web server does not fully parse requested URLs before it examines them for authorization, it may be possible for an attacker to bypass authorization protection.

      Entry at MITRE CWE-551

    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 modifiedEEF

      Description added or changed

      Show 21 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionchanged
      Incorrect Authorization vulnerability in Erlang OTP (inets modules) allows unauthenticated access to CGI scripts protected by directory rules when served via script_alias. When script_alias maps a URL prefix to a directory outside DocumentRoot, mod_auth evaluates directory-based access controls against the DocumentRoot-relative path while mod_cgi executes the script at the ScriptAlias-resolved path. This path mismatch allows unauthenticated access to CGI scripts that directory rules were meant to protect. This vulnerability is associated with program files lib/inets/src/http_server/mod_alias.erl, lib/inets/src/http_server/mod_auth.erl, and lib/inets/src/http_server/mod_cgi.erl. This issue affects OTP from OTP 17.0 before OTP 28.4.2, OTP 27.3.4.10 and OTP 26.2.5.19, corresponding to inets from 5.10 before 9.6.2, 9.3.2.4 and 9.1.0.6.
      Incorrect Authorization vulnerability in Erlang OTP (inets modules) allows unauthenticated access to CGI scripts protected by directory rules when served via script_alias. When script_alias maps a URL prefix to a directory outside DocumentRoot, mod_auth evaluates directory-based access controls against the DocumentRoot-relative path while mod_cgi executes the script at the ScriptAlias-resolved path. This path mismatch allows unauthenticated access to CGI scripts that directory rules were meant to protect. This vulnerability is associated with program files lib/inets/src/http_server/mod_alias.erl, lib/inets/src/http_server/mod_auth.erl, and lib/inets/src/http_server/mod_cgi.erl. This issue affects OTP from OTP 17.0 before OTP 26.2.5.19, OTP 27.3.4.10, and OTP 28.4.2, corresponding to inets from 5.10 before 9.1.0.6, 9.3.2.4, and 9.6.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/28xxx/CVE-2026-28808.json">CVE-2026-28808</a>
      Referenceadded
      —
      https://cna.erlef.org/cves/CVE-2026-28808.html
      Referenceadded
      —
      https://github.com/erlang/otp/commit/07b8f441ca711f9812fad9e9115bab3c3aa92f79
      Referenceadded
      —
      https://github.com/erlang/otp/commit/8fc71ac6af4fbcc54103bec2983ef22e82942688
      Referenceadded
      —
      https://github.com/erlang/otp/commit/9dfa0c51eac97866078e808dec2183cb7871ff7c
      Referenceadded
      —
      https://github.com/erlang/otp/security/advisories/GHSA-3vhp-h532-mc3f
      Referenceadded
      —
      https://osv.dev/vulnerability/EEF-CVE-2026-28808
      Referenceadded
      —
      https://www.erlang.org/doc/system/versions.html#order-of-versions
      Referenceremoved
      https://cna.erlef.org/cves/CVE-2026-28808.html
      —
      Referenceremoved
      https://github.com/erlang/otp/commit/8fc71ac6af4fbcc54103bec2983ef22e82942688
      —
      Referenceremoved
      https://github.com/erlang/otp/commit/9dfa0c51eac97866078e808dec2183cb7871ff7c
      —
      Referenceremoved
      https://github.com/erlang/otp/security/advisories/GHSA-3vhp-h532-mc3f
      —
      Referenceremoved
      https://osv.dev/vulnerability/EEF-CVE-2026-28808
      —
      Referenceremoved
      https://www.erlang.org/doc/system/versions.html#order-of-versions
      —
      Reference typeremoved
      https://cna.erlef.org/cves/CVE-2026-28808.html Types: Mitigation, Vendor Advisory
      —
      Reference typeremoved
      https://github.com/erlang/otp/commit/8fc71ac6af4fbcc54103bec2983ef22e82942688 Types: Patch
      —
      Reference typeremoved
      https://github.com/erlang/otp/commit/9dfa0c51eac97866078e808dec2183cb7871ff7c Types: Patch
      —
      Reference typeremoved
      https://github.com/erlang/otp/security/advisories/GHSA-3vhp-h532-mc3f Types: Third Party Advisory
      —
      Reference typeremoved
      https://osv.dev/vulnerability/EEF-CVE-2026-28808 Types: Patch, Third Party Advisory
      —
      Reference typeremoved
      https://www.erlang.org/doc/system/versions.html#order-of-versions Types: Product
      —

      Source identifier: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

    2. Record modifiedRed Hat ADP

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://access.redhat.com/security/cve/CVE-2026-28808
      Referenceadded
      —
      https://bugzilla.redhat.com/show_bug.cgi?id=2455909
      Referenceadded
      —
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-28808.json
      Referenceremoved
      https://access.redhat.com/security/cve/CVE-2026-28808
      —
      Referenceremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2455909
      —
      Referenceremoved
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-28808.json
      —

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    3. Record modifiedEEF

      Description added or changed

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionchanged
      Incorrect Authorization vulnerability in Erlang OTP (inets modules) allows unauthenticated access to CGI scripts protected by directory rules when served via script_alias. When script_alias maps a URL prefix to a directory outside DocumentRoot, mod_auth evaluates directory-based access controls against the DocumentRoot-relative path while mod_cgi executes the script at the ScriptAlias-resolved path. This path mismatch allows unauthenticated access to CGI scripts that directory rules were meant to protect. This vulnerability is associated with program files lib/inets/src/http_server/mod_alias.erl, lib/inets/src/http_server/mod_auth.erl, and lib/inets/src/http_server/mod_cgi.erl. This issue affects OTP from OTP 17.0 until OTP 28.4.2, 27.3.4.10 and 26.2.5.19 corresponding to inets from 5.10 until 9.6.2, 9.3.2.4 and 9.1.0.6.
      Incorrect Authorization vulnerability in Erlang OTP (inets modules) allows unauthenticated access to CGI scripts protected by directory rules when served via script_alias. When script_alias maps a URL prefix to a directory outside DocumentRoot, mod_auth evaluates directory-based access controls against the DocumentRoot-relative path while mod_cgi executes the script at the ScriptAlias-resolved path. This path mismatch allows unauthenticated access to CGI scripts that directory rules were meant to protect. This vulnerability is associated with program files lib/inets/src/http_server/mod_alias.erl, lib/inets/src/http_server/mod_auth.erl, and lib/inets/src/http_server/mod_cgi.erl. This issue affects OTP from OTP 17.0 before OTP 28.4.2, OTP 27.3.4.10 and OTP 26.2.5.19, corresponding to inets from 5.10 before 9.6.2, 9.3.2.4 and 9.1.0.6.

      Source identifier: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

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