HighCVE-2026-59251

    Denial of service via exponential certificate policy tree growth in path validation (CVE-2026-59251)

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

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    What is affected, what to do

    Allocation of resources without limits in Erlang/OTP public_key certificate path validation allows a remote unauthenticated attacker to cause denial of service by sending a crafted X.509 certificate chain during the TLS handshake. During RFC 5280 policy processing in public_key:pkix_path_validation/3, the certificate policy tree maintained by pubkey_policy_tree grows without an upper bound.

    Update erlang\/otp to version 27.3.4.15, erlang\/public_key to version 1.17.1.5, Erlang/OTP to version 28.5.0.4.

    Affected
    • Erlang OTP gte 1.15..*
    • Erlang OTP gte 26.2..*

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

    Metrics

    8.7

    Priority

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

    Source: NVD, CVSS v4

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

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

    0.3 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 25.0

    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
    69.62 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
    8.7 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
    7.5
    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
    8.7
    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
    25.0
    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 · automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 27 July 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-770

    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

    Allocation of resources without limits in Erlang/OTP public_key certificate path validation allows a remote unauthenticated attacker to cause denial of service by sending a crafted X.509 certificate chain during the TLS handshake. During RFC 5280 policy processing in public_key:pkix_path_validation/3, the certificate policy tree maintained by pubkey_policy_tree grows without an upper bound. When a certificate chain contains M policies per certificate and K certificates, the tree grows on the order of M^K nodes because pubkey_policy_tree:add_leaves/2 and pubkey_policy_tree:add_leaf_siblings/2 extend the tree per policy per certificate. A modest chain with many policies per certificate is enough to pin BEAM schedulers and exhaust the node's memory, taking down the entire VM. The attacker only needs to be able to present a certificate chain to the victim, which is the normal precondition for a TLS handshake, so exploitation succeeds against any incoming or outgoing TLS connection that validates the peer's chain (the default for SSL/TLS clients and mutual-TLS servers). This is the same vulnerability class as OpenSSL's X509_verify_cert policy tree DoS. This vulnerability is associated with program files lib/public_key/src/pubkey_policy_tree.erl and program routines pubkey_policy_tree:add_leaves/2 and pubkey_policy_tree:add_leaf_siblings/2. This issue affects OTP from OTP 26.2 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15, corresponding to public_key from 1.15 before 1.21.4, 1.20.3.4 and 1.17.1.5.

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

    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
    • ≥ 26.2
    • ≥ 1.15
    • —
    • —
    erlangerlang\/otp
    • 26.2 – < 27.3.4.15
    • 28.0 – < 28.5.0.4
    • 29.0 – < 29.0.4
    • 27.3.4.15
    • 28.5.0.4
    • 29.0.4
    erlangerlang\/public_key
    • 1.15 – < 1.17.1.5
    • 1.21 – < 1.21.4
    • 1.18 – < 1.20.3.4
    • 1.17.1.5
    • 1.21.4
    • 1.20.3.4
    Open SourceErlang/OTP
    • < 28.5.0.4
    • < 27.3.4.15
    • < 29.0.4
    • 28.5.0.4
    • 27.3.4.15
    • 29.0.4

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianerlangtrixie
    Linuxubuntuerlangbionic
    Linuxubuntuerlangfocal
    Linuxubuntuerlangjammy
    Linuxubuntuerlangnoble
    Linuxubuntuerlangresolute
    Linuxubuntuerlangtrusty
    Linuxubuntuerlangxenial

    Weakness classes (CWE)

    • CWE-770Allocation of Resources Without Limits or Throttling

      Base

      The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

      Entry at MITRE CWE-770

    References & sources

    • github.comerlang/otp/security/advisories/GHSA-622p-qfh6-c352advisory, Vendor advisory, related, Vendor advisory
    • cna.erlef.orgcves/CVE-2026-59251.htmlweb, related, Patch, Third-party advisory
    • erlang.orgdoc/system/versions.htmlweb, x_version-scheme, Release notes
    • github.comerlang/otp/commit/f8580fc117098c08165f46c26fd0750c5cfb2a90fix, Patch, Patch
    • github.comerlang/otp/commit/f04c6bba38de1cf1b1836a7d9a9fbe239bd939e8fix, Patch, Patch
    • OSV (Open Source Vulnerabilities)vulnerability/EEF-CVE-2026-59251related, Patch, Third-party 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. Initial analysis by NVDNVD

      Newly listed as affected:
      • erlang/otp (26.2 – before 27.3.4.15; 28.0 – before 28.5.0.4; 29.0 – before 29.0.4)
      • erlang/public key (1.15 – before 1.17.1.5; 1.18 – before 1.20.3.4; 1.21 – before 1.21.4)

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

      Show 8 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
      Product configurationadded
      —
      OR *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 26.2 up to (excluding) 27.3.4.15 *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 28.0 up to (excluding) 28.5.0.4 *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 29.0 up to (excluding) 29.0.4 *cpe:2.3:a:erlang:erlang/public_key:*:*:*:*:*:*:*:* versions from (including) 1.15 up to (excluding) 1.17.1.5 *cpe:2.3:a:erlang:erlang/public_key:*:*:*:*:*:*:*:* versions from (including) 1.18 up to (excluding) 1.20.3.4 *cpe:2.3:a:erlang:erlang/public_key:*:*:*:*:*:*:*:* versions from (including) 1.21 up to (excluding) 1.21.4
      Reference typeadded
      —
      EEF: https://cna.erlef.org/cves/CVE-2026-59251.html Types: Patch, Third Party Advisory
      Reference typeadded
      —
      EEF: https://github.com/erlang/otp/commit/f04c6bba38de1cf1b1836a7d9a9fbe239bd939e8 Types: Patch
      Reference typeadded
      —
      EEF: https://github.com/erlang/otp/commit/f8580fc117098c08165f46c26fd0750c5cfb2a90 Types: Patch
      Reference typeadded
      —
      EEF: https://github.com/erlang/otp/security/advisories/GHSA-622p-qfh6-c352 Types: Vendor Advisory
      Reference typeadded
      —
      EEF: https://osv.dev/vulnerability/EEF-CVE-2026-59251 Types: Patch, Third Party Advisory
      Reference typeadded
      —
      EEF: https://www.erlang.org/doc/system/versions.html#order-of-versions Types: Release Notes

      Source identifier: nvd@nist.gov

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: yes

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-59251","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-07-27T18:31:50.981990Z"}

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

    3. ReceivedEEF

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

      Weakness type: CWE-770

      Description added or changed

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      OTP, OTP
      Descriptionadded
      —
      Allocation of resources without limits in Erlang/OTP public_key certificate path validation allows a remote unauthenticated attacker to cause denial of service by sending a crafted X.509 certificate chain during the TLS handshake. During RFC 5280 policy processing in public_key:pkix_path_validation/3, the certificate policy tree maintained by pubkey_policy_tree grows without an upper bound. When a certificate chain contains M policies per certificate and K certificates, the tree grows on the order of M^K nodes because pubkey_policy_tree:add_leaves/2 and pubkey_policy_tree:add_leaf_siblings/2 extend the tree per policy per certificate. A modest chain with many policies per certificate is enough to pin BEAM schedulers and exhaust the node's memory, taking down the entire VM. The attacker only needs to be able to present a certificate chain to the victim, which is the normal precondition for a TLS handshake, so exploitation succeeds against any incoming or outgoing TLS connection that validates the peer's chain (the default for SSL/TLS clients and mutual-TLS servers). This is the same vulnerability class as OpenSSL's X509_verify_cert policy tree DoS. This vulnerability is associated with program files lib/public_key/src/pubkey_policy_tree.erl and program routines pubkey_policy_tree:add_leaves/2 and pubkey_policy_tree:add_leaf_siblings/2. This issue affects OTP from OTP 26.2 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15, corresponding to public_key from 1.15 before 1.21.4, 1.20.3.4 and 1.17.1.5.
      CVSSadded
      —
      AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/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-770
      Referenceadded
      —
      https://cna.erlef.org/cves/CVE-2026-59251.html
      Referenceadded
      —
      https://github.com/erlang/otp/commit/f04c6bba38de1cf1b1836a7d9a9fbe239bd939e8
      Referenceadded
      —
      https://github.com/erlang/otp/commit/f8580fc117098c08165f46c26fd0750c5cfb2a90
      Referenceadded
      —
      https://github.com/erlang/otp/security/advisories/GHSA-622p-qfh6-c352
      Referenceadded
      —
      https://osv.dev/vulnerability/EEF-CVE-2026-59251
      Referenceadded
      —
      https://www.erlang.org/doc/system/versions.html#order-of-versions

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

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