---
id: CVE-2026-80218
title: >-
  Improper Authentication vulnerability in team-alembic AshAuthentication allows
  an attacker holding a sign-in token for one authenticated resource to be
  signed in as a user of a different resource.


  AshAuthentication.Strategy.Password.Sig…
summary: >-
  Improper Authentication vulnerability in team-alembic AshAuthentication allows
  an attacker holding a sign-in token for one authenticated resource to be
  signed in as a user of a different resource.


  AshAuthentication.Strategy.Password.Sig…
severity: high
cvss: 7.6
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'
cwe:
  - CWE-287
vendor: team-alembic
product: ash_authentication
affected:
  - ash_authentication >= 3.10.5 < 4.15.0
  - ash_authentication >= 5.0.0-rc.0 < 5.0.0-rc.14
  - >-
    team-alembic/ash_authentication >= eca8cadea0f1595ed2c10a0c177b1da9aa9e5269
    < *
published: '2026-09-17'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T18:16:18.527'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-80218'
references:
  - url: 'https://cna.erlef.org/cves/CVE-2026-80218.html'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/2640e1872e1fef4e4606e601bf00102cff784c03
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/7baac243ca651eee127a84d672eee3fcff42e598
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/eca8cadea0f1595ed2c10a0c177b1da9aa9e5269
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-3pr8-f99q-86hp
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-80218'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
tags:
  - nvd
  - cve.org
epss: 0.00637
epssPercentile: 0.48411
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-17T18:28:40.896413Z'
cvssSource: cna
ingestedAt: '2026-09-17T13:18:16.986Z'
---

## Overview

Improper Authentication vulnerability in team-alembic AshAuthentication allows an attacker holding a sign-in token for one authenticated resource to be signed in as a user of a different resource.

AshAuthentication.Strategy.Password.SignInWithTokenPreparation.extract_primary_keys_from_subject/2 parses the JWT sub claim (for example user?id=1) with URI.parse/1 and keeps only its query string, discarding the path segment that names the subject the token was issued for. Nothing else restores that binding: AshAuthentication.Jwt.verify/3 checks the signature, exp, nbf, jti and the library-version claims, the purpose check only requires sign_in, and the remaining comparison is over primary-key field names, which are identical across resources. The WebAuthn sign-in and remember-me preparations carry copies of the same helper and drop the path in the same way. The magic link sign-in path pins the subject name against the resource and is not affected.

This issue affects ash_authentication: from 3.10.5 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.