CVE-2026-82761 team-alembic CVE debrief

Who should care

Defenders responsible for authentication and authorization mechanisms, as well as developers using AshAuthentication in their applications, should assess exposure and prioritize verification and remediation.

Why it matters

A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in team-alembic AshAuthentication allows an attacker holding a leaked magic link to replay its single-use token and authenticate as the target subject, which can lead to unauthorized access and sensitive information disclosure.

• An attacker can authenticate as the target subject using a leaked single-use token.
• The vulnerability allows for unauthorized access to sensitive information and systems.
• Defenders must verify and upgrade to a fixed version of ash_authentication to prevent exploitation.
• Remediation priority is high due to the critical severity of the vulnerability.

Technical summary

The vulnerability is caused by a TOCTOU race condition in AshAuthentication, which allows an attacker to replay a single-use token and authenticate as the target subject. The issue affects ash_authentication versions from 3.9.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14. This can lead to unauthorized access and sensitive information disclosure. Defenders should prioritize verifying and upgrading to a fixed version of ash_authentication to prevent exploitation. The vulnerability arises from a race condition between the verification and revocation of single-use tokens.

Defensive priority

Defenders should prioritize verifying and upgrading to a fixed version of ash_authentication, as the vulnerability allows for unauthorized authentication.

Recommended defensive actions

• Verify the version of ash_authentication and upgrade to a fixed version (4.15.0 or later, or 5.0.0-rc.14 or later) to prevent unauthorized authentication.
• Implement additional authentication mechanisms to prevent replay attacks.
• Monitor for suspicious authentication attempts and revoke access as needed.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The vulnerability is caused by a TOCTOU race condition in AshAuthentication, which allows an attacker to replay a single-use token and authenticate as the target subject. This issue is exacerbated by the fact that the token's validity check is not serialized against its consumption, allowing concurrent redemptions to succeed. The affected versions of ash_authentication are from 3.9.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14. Defenders should verify the version of ash_authentication and upgrade to a fixed version to prevent

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.