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CVE-2026-76949

CriticalCVSS 9.1 / 10
Published Sep 17, 2026·Last modified Sep 19, 2026
Affected Components(28)
team-alembic/ash_authentication
4.13.6
team-alembic/ash_authentication
4.13.3
team-alembic/ash_authentication
4.10.0
1 / 10
Description

Authentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who can plant a remember-me cookie in a victim's browser to replace that victim's authenticated session with one for the attacker's own account.

AshAuthentication.Plug.Helpers.sign_in_using_remember_me/3 skips re-authenticating an already-signed-in visitor by checking the session for "<subject_name>_token", but store_in_session/2 writes that key only when require_token_presence_for_authentication? is enabled and otherwise writes the bare subject name. At the default setting the guard therefore reads a key that is never written, its already-signed-in branch is unreachable, and the remember-me sign-in runs on every request through the per-request browser pipeline plug. A planted remember-me cookie is consequently honoured even for a visitor holding a live authenticated session, so whatever the victim enters afterwards lands in data the attacker controls. The read path in authenticate_resource_from_session/4 selects the key correctly, so the guard and the reader disagree about which key holds the session.

This issue affects ash_authentication: from 4.10.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

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Risk Scores
Base Score
9.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.

Threat Intelligence
6.9

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.77%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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