---
id: CVE-2026-88952
title: >-
  Improper Authentication vulnerability in team-alembic AshAuthentication allows
  an attacker to be signed in as another user by linking an OAuth2 identity to
  an account that is not theirs.


  AshAuthentication.Strategy.OAuth2.UserResolver.re…
summary: >-
  Improper Authentication vulnerability in team-alembic AshAuthentication allows
  an attacker to be signed in as another user by linking an OAuth2 identity to
  an account that is not theirs.


  AshAuthentication.Strategy.OAuth2.UserResolver.re…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/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 >= 4.14.0 < 4.15.0
  - ash_authentication >= 5.0.0-rc.10 < 5.0.0-rc.14
  - >-
    team-alembic/ash_authentication >= 64530644f9b37ebb76ca14aeb83a77597a0034b7
    < *
  - >-
    team-alembic/ash_authentication >= 42edcd8ebb13fafbb168f12591d7518ce0611fec
    < *
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-2026-88952'
references:
  - url: 'https://cna.erlef.org/cves/CVE-2026-88952.html'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/2bd630eef8b7c8ae1e90e8fd43ba12fbc7e256ba
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/42edcd8ebb13fafbb168f12591d7518ce0611fec
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/64530644f9b37ebb76ca14aeb83a77597a0034b7
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/commit/738bf9f32f2aa0d1bb92ce9ca5c2476cb5710459
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-wc6x-276q-jrf9
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-88952'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
tags:
  - nvd
  - cve.org
epss: 0.00749
epssPercentile: 0.52958
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-17T19:32:22.090404Z'
cvssSource: cna
ingestedAt: '2026-09-17T15:20:39.001Z'
---

## Overview

Improper Authentication vulnerability in team-alembic AshAuthentication allows an attacker to be signed in as another user by linking an OAuth2 identity to an account that is not theirs.

AshAuthentication.Strategy.OAuth2.UserResolver.resolve/3 matches an existing account using the register action's upsert_identity keys, then gates linking the incoming provider identity to it on email_trusted?/2, which reads only the provider's email_verified boolean and never compares the provider's email value with the matched account's email. That gate assumes the account was matched by its email field, so under any other upsert_identity it is vacuous and an attacker presenting their own verified email is attached to, and issued a session for, an account matched on some other attribute. The same unguarded gate applies in OAuth2.SignInPreparation on the registration_enabled? false path, where the account is matched by the sign-in action's read filter instead. The upsert also rewrites the matched account's email to the attacker's address, so later account recovery reaches the attacker rather than the owner.

This issue affects ash_authentication: from 4.14.0 before 4.15.0 and from 5.0.0-rc.10 before 5.0.0-rc.14.

## Remediation

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