Account takeover via purpose-unchecked bearer JWT
Published Aug 25, 2026 · Updated Aug 25, 2026
Authentication bypass in Alembic Ash Authentication 3.10.5 through 4.14.1 and 5.0.0-rc.0 through 5.0.0-rc.12 lets remote attackers impersonate users. AshAuthentication.Plug.Helpers.retrieve_from_bearer/3 verifies the JWT signature but never requires purpose == "user", while stateless validate_token/3 skips the token store. Exploitation requires a still-valid sign-in token, a reachable bearer-enabled route, stateless token verification, and WebAuthn or enabled Password sign-in tokens; successful replay assigns the victim as current_user with full application privileges.
Summary
What happened
Authentication bypass in Alembic Ash Authentication 3.10.5 through 4.14.1 and 5.0.0-rc.0 through 5.0.0-rc.12 lets remote attackers impersonate users. AshAuthentication.Plug.Helpers.retrieve_from_bearer/3 verifies the JWT signature but never requires purpose == "user", while stateless validate_token/3 skips the token store. Exploitation requires a still-valid sign-in token, a reachable bearer-enabled route, stateless token verification, and WebAuthn or enabled Password sign-in tokens; successful replay assigns the victim as current_user with full application privileges.
The record
- CVE
- CVE-2026-65633
- Published
- Aug 25, 2026
- Updated
- Aug 25, 2026
- Vendor
- Alembic
- Product
- Ash Authentication
- Classifications
- CWE-287, T1550.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 25, 2026CVE publishedPublication date reported by the CVE source.
- Aug 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=3.10.5 <4.14.2
- Affected versionversion=5.0.0-rc.0 <5.0.0-rc.13
- Affected versionversion=eca8cadea0f1595ed2c10a0c177b1da9aa9e5269 <* changes=[{"at":"8cf8b2d4426172be0900a3505e9491800b951750","status":"unaffected"},{"at":"124eddd1bbeb40289c3fe8831ac10677a19fcf09","status":"unaffected"}]
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Upstream sign-in JWT replay reproductionproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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