MediumCVE-2026-78223

    Token revocation record built from unverified JWT claims in AshAuthentication (CVE-2026-78223)

    Published Last modified Sources: OSV, CVE.org

    Share

    What is affected, what to do

    Improper Verification of Cryptographic Signature vulnerability in team-alembic AshAuthentication allows a caller of the token revocation action to neutralise a revocation or write arbitrary rows into the token resource. AshAuthentication.TokenResource.RevokeTokenChange.change/3 reads the :token argument and decodes it with AshAuthentication.Jwt.peek/1, which delegates to Joken.peek_claims/1 and performs no signature check, unlike Jwt.verify/4.

    Update Team-alembic Ash Authentication to version 4.15.0, Team-alembic Ash Authentication to version 5.0.0-rc.14.

    Affected
    • Team-alembic Ash Authentication lt 0.2.0..4.15.0
    • Team-alembic Ash Authentication lt 5.0.0-rc.0..5.0.0-rc.14
    Fixed in
    • Team-alembic Ash Authentication 4.15.0
    • Team-alembic Ash Authentication 5.0.0-rc.14

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

    Metrics

    6.9

    Priority

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

    Source: Vendor (CNA), CVSS v4

    6.9

    CVSS v4

    Severity Medium on the scale from 0 to 10.

    Source: OSV, CVE.org

    0.4 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 38.5

    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
    72.71 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
    6.9 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
    6.9
    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
    38.5
    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 17 September 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-347

    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

    Improper Verification of Cryptographic Signature vulnerability in team-alembic AshAuthentication allows a caller of the token revocation action to neutralise a revocation or write arbitrary rows into the token resource. AshAuthentication.TokenResource.RevokeTokenChange.change/3 reads the :token argument and decodes it with AshAuthentication.Jwt.peek/1, which delegates to Joken.peek_claims/1 and performs no signature check, unlike Jwt.verify/4. The jti, exp and sub claims it returns are written straight onto the revocation record, guarded only by byte_size(token) > 0. Because expires_at derives from the attacker-chosen exp, a forged copy of a genuine token that keeps the real jti but backdates exp yields a revocation row that is already expired: expunge_expired removes it and the genuine token passes revoked? again. Arbitrary jti and sub values can be inserted the same way. This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

    Source: OSV (Open Source Vulnerabilities), NVD (NIST), cvelistv5

    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
    team-alembicash_authentication
    • 0.2.0 – < 4.15.0
    • 5.0.0-rc.0 – < 5.0.0-rc.14
    • 4.15.0
    • 5.0.0-rc.14
    hexash_authentication
    • 3.9.4
    • 4.13.2
    • 4.9.6
    • 4.3.5
    • 4.7.1
    • 4.2.2
    • 4.9.9
    • 4.14.2
    • 4.1.0
    • 4.3.3
    • 4.0.0-rc.1
    • 3.12.4
    • 4.2.7
    • 4.4.0
    • 0.2.0
    • 4.0.0-rc.6
    • 3.5.2
    • 4.4.9
    • 4.13.5
    • 5.0.0-rc.5
    • 4.7.2
    • 3.10.0
    • 4.9.0
    • 4.6.4
    • 4.5.6
    • 4.3.2
    • 4.0.0-rc.5
    • 3.10.1
    • 4.8.2
    • 5.0.0-rc.7
    • 5.0.0-rc.6
    • 4.3.7
    • 4.6.2
    • 4.8.7
    • 4.14.1
    • 4.6.3
    • 4.0.4
    • 3.9.6
    • 3.7.8
    • 3.2.1
    • 3.11.11
    • 4.8.6
    • 3.10.2
    • 4.9.1
    • 5.0.0-rc.3
    • 3.11.3
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-347Improper Verification of Cryptographic Signature

      Base

      The product does not verify, or incorrectly verifies, the cryptographic signature for data.

      Entry at MITRE CWE-347

    References & sources

    • github.comteam-alembic/ash_authentication/security/advisories/GHSA-mfwg-5…related, Vendor advisory
    • cna.erlef.orgEEF CNA record for CVE-2026-78223related
    • OSV (Open Source Vulnerabilities)OSV record EEF-CVE-2026-78223related
    • github.comIntroducing commit a939dde in team-alembic/ash_authenticationrelated
    • github.comFix commit 344cebb in team-alembic/ash_authenticationPatch
    • github.comFix commit eb86353 in team-alembic/ash_authenticationPatch
    • hex.pmpackages/ash_authenticationpackage

    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: yes

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-78223","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-09-17T18:28:12.763636Z"}

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

    2. ReceivedEEF

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

      Weakness type: CWE-347

      Description added or changed

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      Improper Verification of Cryptographic Signature vulnerability in team-alembic AshAuthentication allows a caller of the token revocation action to neutralise a revocation or write arbitrary rows into the token resource. AshAuthentication.TokenResource.RevokeTokenChange.change/3 reads the :token argument and decodes it with AshAuthentication.Jwt.peek/1, which delegates to Joken.peek_claims/1 and performs no signature check, unlike Jwt.verify/4. The jti, exp and sub claims it returns are written straight onto the revocation record, guarded only by byte_size(token) > 0. Because expires_at derives from the attacker-chosen exp, a forged copy of a genuine token that keeps the real jti but backdates exp yields a revocation row that is already expired: expunge_expired removes it and the genuine token passes revoked? again. Arbitrary jti and sub values can be inserted the same way. This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.
      CVSSadded
      —
      AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/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-347
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/78xxx/CVE-2026-78223.json">CVE-2026-78223</a>
      Referenceadded
      —
      https://cna.erlef.org/cves/CVE-2026-78223.html
      Referenceadded
      —
      https://github.com/team-alembic/ash_authentication/commit/344cebb12faf68e648d3283394073ba0c0f78459
      Referenceadded
      —
      https://github.com/team-alembic/ash_authentication/commit/a939dde9b917c072cdf10c4b0913a9886a4b0231
      Referenceadded
      —
      https://github.com/team-alembic/ash_authentication/commit/eb86353fe5a547c5ff5fd9af0e2c212518c31c9b
      Referenceadded
      —
      https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-mfwg-5cpf-px58
      Referenceadded
      —
      https://osv.dev/vulnerability/EEF-CVE-2026-78223

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

    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-2026-78223
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-78223"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-78223.svg?lang=en" alt="CVE-2026-78223 – NEOSEC Intel" height="20"></a>