HighCVE-2026-55737

    Erlang OTP: Signed to Unsigned Conversion Error (CVE-2026-55737)

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

    What is affected, what to do

    Signed to Unsigned Conversion Error and Out-of-bounds Write vulnerability in Erlang OTP erts allows an attacker who can supply a crafted Erlang external term format (ETF) binary to binary_to_term/1 to corrupt the BEAM heap pointer and crash the virtual machine. When decoding a LARGE_TUPLE_EXT term, the validation pass decoded_size() in erts/emulator/beam/external.c reads the 32-bit arity field as unsigned (get_uint32()), while the decode pass dec_term() reads the same field as a signed 32-bit integer (get_int32()) into an int.

    Update erlang\/otp to version 27.3.4.15, erts to version 16.4.0.4, Erlang/OTP to version 28.5.0.4.

    Affected
    • Erlang OTP gte 13.0..*
    • Erlang OTP gte 25.0..*

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

    Metrics

    7.5

    Priority

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

    Source: NVD, CVSS v3

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

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

    0.3 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 21.3

    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
    62.82 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
    7.5 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
    5.1
    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
    21.3
    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: 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-195, CWE-787

    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

    Signed to Unsigned Conversion Error and Out-of-bounds Write vulnerability in Erlang OTP erts allows an attacker who can supply a crafted Erlang external term format (ETF) binary to binary_to_term/1 to corrupt the BEAM heap pointer and crash the virtual machine. When decoding a LARGE_TUPLE_EXT term, the validation pass decoded_size() in erts/emulator/beam/external.c reads the 32-bit arity field as unsigned (get_uint32()), while the decode pass dec_term() reads the same field as a signed 32-bit integer (get_int32()) into an int. An arity wire value of 0x80000000 passes validation as 2147483648 but decodes as -2147483648, so the subsequent hp += n moves the heap allocation pointer backward. Neither pass enforces the runtime tuple-arity limit MAX_ARITYVAL. The result is an out-of-bounds heap write; in practice the VM detects an impossible heap size and aborts, denying service. The required padding is large when uncompressed but the compressed-ETF envelope shrinks it to a small payload on the wire. This issue affects OTP from OTP 25.0 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15, corresponding to erts from 13.0 before 17.0.4, 16.4.0.4 and 15.2.7.11.

    Source: Ubuntu Security Notices, suse_csaf, Debian Security Advisories, BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST), Microsoft Security Update Guide, OSV (Open Source Vulnerabilities), 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
    ErlangOTP
    • ≥ 13.0
    • ≥ 25.0
    • —
    • —
    erlangerlang\/otp
    • 25.0 – < 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
    erlangerts
    • 16.0 – < 16.4.0.4
    • 13.0 – < 15.2.7.11
    • 17.0 – < 17.0.4
    • 16.4.0.4
    • 15.2.7.11
    • 17.0.4
    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-195Signed to Unsigned Conversion Error

      Variant

      The product uses a signed primitive and performs a cast to an unsigned primitive, which can produce an unexpected value if the value of the signed primitive can not be represented using an unsigned primitive.

      Entry at MITRE CWE-195

    • CWE-787Out-of-bounds Write

      Base

      The product writes data past the end, or before the beginning, of the intended buffer.

      Entry at MITRE CWE-787

    References & sources

    • github.comerlang/otp/security/advisories/GHSA-446w-268v-9462advisory, Vendor advisory, related, Vendor advisory
    • cna.erlef.orgcves/CVE-2026-55737.htmlweb, related, Patch, Third-party advisory
    • erlang.orgdoc/system/versions.htmlweb, x_version-scheme, Release notes
    • github.comerlang/otp/commit/c5210b42a9d3d96f3d25601942ce8122be0f3761fix, Patch, Patch
    • OSV (Open Source Vulnerabilities)vulnerability/EEF-CVE-2026-55737related, 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 (28.0 – before 28.5.0.4; 29.0 – before 29.0.4; 25.0 – before 27.3.4.15)
      • Erlang Runtime System (ERTS) (16.0 – before 16.4.0.4; 17.0 – before 17.0.4; 13.0 – before 15.2.7.11)

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

      Show 7 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) 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:erts:*:*:*:*:*:*:*:* versions from (including) 16.0 up to (excluding) 16.4.0.4 *cpe:2.3:a:erlang:erts:*:*:*:*:*:*:*:* versions from (including) 17.0 up to (excluding) 17.0.4 *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 25.0 up to (excluding) 27.3.4.15 *cpe:2.3:a:erlang:erts:*:*:*:*:*:*:*:* versions from (including) 13.0 up to (excluding) 15.2.7.11
      Reference typeadded
      —
      EEF: https://cna.erlef.org/cves/CVE-2026-55737.html Types: Patch, Third Party Advisory
      Reference typeadded
      —
      EEF: https://github.com/erlang/otp/commit/c5210b42a9d3d96f3d25601942ce8122be0f3761 Types: Patch
      Reference typeadded
      —
      EEF: https://github.com/erlang/otp/security/advisories/GHSA-446w-268v-9462 Types: Vendor Advisory
      Reference typeadded
      —
      EEF: https://osv.dev/vulnerability/EEF-CVE-2026-55737 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: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-55737","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-07-27T18:34:45.698069Z"}

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

    3. ReceivedEEF

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

      Weakness type: CWE-787, CWE-195

      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
      —
      Signed to Unsigned Conversion Error and Out-of-bounds Write vulnerability in Erlang OTP erts allows an attacker who can supply a crafted Erlang external term format (ETF) binary to binary_to_term/1 to corrupt the BEAM heap pointer and crash the virtual machine. When decoding a LARGE_TUPLE_EXT term, the validation pass decoded_size() in erts/emulator/beam/external.c reads the 32-bit arity field as unsigned (get_uint32()), while the decode pass dec_term() reads the same field as a signed 32-bit integer (get_int32()) into an int. An arity wire value of 0x80000000 passes validation as 2147483648 but decodes as -2147483648, so the subsequent hp += n moves the heap allocation pointer backward. Neither pass enforces the runtime tuple-arity limit MAX_ARITYVAL. The result is an out-of-bounds heap write; in practice the VM detects an impossible heap size and aborts, denying service. The required padding is large when uncompressed but the compressed-ETF envelope shrinks it to a small payload on the wire. This issue affects OTP from OTP 25.0 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15, corresponding to erts from 13.0 before 17.0.4, 16.4.0.4 and 15.2.7.11.
      CVSSadded
      —
      AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/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-787
      Weakness type (CWE)added
      —
      CWE-195
      Referenceadded
      —
      https://cna.erlef.org/cves/CVE-2026-55737.html
      Referenceadded
      —
      https://github.com/erlang/otp/commit/c5210b42a9d3d96f3d25601942ce8122be0f3761
      Referenceadded
      —
      https://github.com/erlang/otp/security/advisories/GHSA-446w-268v-9462
      Referenceadded
      —
      https://osv.dev/vulnerability/EEF-CVE-2026-55737
      Referenceadded
      —
      https://www.erlang.org/doc/system/versions.html#order-of-versions

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

    One NVD translation into another language is hidden.

    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2026-55737
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-55737"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-55737.svg?lang=en" alt="CVE-2026-55737 – NEOSEC Intel" height="20"></a>