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Vulnerability · Published Sep 17, 2026 · Assigned by EEF

CVE-2026-81637Replayable OAuth2 CSRF state retained after a failed callback in AshAuthentication

Low 2.3

In plain English

A low-severity security flaw in ash_authentication from team-alembic. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 49% of all known vulnerabilities).

Severity (CVSS 4.0)2.3Low
Exploit odds (30 days)0.6%top 50.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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.

Affected products (as reported)

VendorProductVersions
team-alembic ash_authentication 0.6.0 – before 4.15.05.0.0-rc.0 – before 5.0.0-rc.14
team-alembic ash_authentication c5f589058e04239263f50a1430eb17ea6d5dd1a2 – before *

Weakness: CWE-613 · Vector: 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

References