---
id: CVE-2026-81637
title: >-
  Insufficient Session Expiration vulnerability in team-alembic
  AshAuthentication allows an attacker who obtains a victim's OAuth2 state value
  to replay the callback and sign that victim into an attacker-controlled
  account.


  AshAuthenticat…
summary: >-
  Insufficient Session Expiration vulnerability in team-alembic
  AshAuthentication allows an attacker who obtains a victim's OAuth2 state value
  to replay the callback and sign that victim into an attacker-controlled
  account.


  AshAuthenticat…
severity: low
cvss: 2.3
cvssVector: 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N'
cwe:
  - CWE-613
vendor: team-alembic
product: ash_authentication
affected:
  - ash_authentication >= 0.6.0 < 4.15.0
  - ash_authentication >= 5.0.0-rc.0 < 5.0.0-rc.14
  - >-
    team-alembic/ash_authentication >= c5f589058e04239263f50a1430eb17ea6d5dd1a2
    < *
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-2026-81637'
references:
  - url: 'https://cna.erlef.org/cves/CVE-2026-81637.html'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/bd4352303bc9d72d007f6818775267585a4bcc2f
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/c5f589058e04239263f50a1430eb17ea6d5dd1a2
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/d7f939cd02bd618bcaa304631846fa75ffc419d7
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-3vcj-gxx8-3p44
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-81637'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
tags:
  - nvd
  - cve.org
epss: 0.00607
epssPercentile: 0.46806
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-17T18:26:48.969731Z'
cvssSource: cna
ingestedAt: '2026-09-17T13:18:16.985Z'
---

## Overview

Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim's OAuth2 state value to replay the callback and sign that victim into an attacker-controlled account.

AshAuthentication.Strategy.OAuth2.Plug.callback/2 clears the stored session_params through a rebinding step inside its with chain, conn <- delete_session(conn, session_key). Elixir evaluates the else block in the scope enclosing the with, so every failure path (the provider returning ?error=access_denied, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches store_authentication_result/2 holding the original connection and the session entry is never removed. The value the module's own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.

This issue affects ash_authentication: from 0.6.0 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.