EUVD-2026-81483Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network-reachable revocation action with no auth guard beyond a non-empty token yields integrity-only impact (defeats revocation/writes bogus rows); no confidentiality or availability effect, so C:N/I:L/A:N.
Primary rating from Vendor (EEF).
CVSS VectorVendor: EEF
Lifecycle Timeline
3DescriptionCVE.org
Improper Verification of Cryptographic Signature vulnerability in team-alembic AshAuthentication allows a caller of the token revocation action to neutralise a revocation or write arbitrary rows into the token resource.
AshAuthentication.TokenResource.RevokeTokenChange.change/3 reads the :token argument and decodes it with AshAuthentication.Jwt.peek/1, which delegates to Joken.peek_claims/1 and performs no signature check, unlike Jwt.verify/4. The jti, exp and sub claims it returns are written straight onto the revocation record, guarded only by byte_size(token) > 0. Because expires_at derives from the attacker-chosen exp, a forged copy of a genuine token that keeps the real jti but backdates exp yields a revocation row that is already expired: expunge_expired removes it and the genuine token passes revoked? again. Arbitrary jti and sub values can be inserted the same way.
This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.
AnalysisAI
AshAuthentication's token-revocation action accepts forged JWTs without verifying their signature, letting an unauthenticated remote caller write arbitrary rows into the token resource or neutralise an existing revocation. Because the revocation record's expires_at is derived from the attacker-supplied exp claim, an attacker holding a copy of a genuine token can resubmit it with the real jti intact but a backdated exp, producing a revocation row that is already expired; once expunge_expired prunes it, the genuine token validates again through revoked? …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires that the target application uses AshAuthentication's TokenResource with the token-revocation action reachable by the attacker, and that the attacker can supply a token value to that action (byte_size(token) > 0 is the only guard). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is an integrity-only weakness (CWE-347) whose real-world priority is moderate-to-low despite a network vector. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade ash_authentication to the fixed releases: 4.15.0 for the stable line or 5.0.0-rc.14 for the 5.0.0 release-candidate line (vendor-released patch; patch availability confirmed by the vendor). … Detailed patch versions, workarounds, and compensating controls in full report. |
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