EUVD-2026-68145Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/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-delivered via browser callback (AV:N); encrypted token support is non-default, mapping AT:P to AC:H; no authentication required (PR:N); victim must initiate the auth flow (UI:R); full account impersonation yields C:H/I:H with no availability impact.
Primary rating from Vendor (EEF).
CVSS VectorVendor: EEF
Lifecycle Timeline
4DescriptionCVE.org
Improper Verification of Cryptographic Signature vulnerability in erlef oidcc allows an unauthenticated attacker to impersonate an arbitrary user via an encrypted ID token or JARM response carrying no nested signature. OpenID Connect Core 1.0 section 2 requires that an encrypted ID token be signed then encrypted, with the result being a Nested JWT, and JARM processing rule 5 requires the client to check the signature unconditionally. oidcc instead accepted a JWE wrapping unsigned claims as fully validated, so anyone holding the relying party's public encryption key could mint a token with an arbitrary sub, iss, and aud without possessing the provider's signing key.
In oidcc_jwt_util:verify_decrypted_token/4, a decrypted payload that is not a signed JWS fell back to parsing the plaintext claims and returning them with no verifying key. oidcc_token:int_validate_jwt/4 then matched on the JOSE structure type rather than on whether a signature had been verified, and returned success. The JARM path in oidcc_token:validate_jarm/3 is reachable through the browser front channel. UserInfo responses are not affected, because OpenID Connect Core 1.0 section 5.3.2 permits them to be encrypted without also being signed.
This issue affects oidcc: from 3.2.0-beta.1 before 3.9.0.
AnalysisAI
Authentication bypass in oidcc (Erlang/Elixir OpenID Connect library) versions 3.2.0-beta.1 through before 3.9.0 allows unauthenticated attackers to impersonate arbitrary users by presenting a JWE-encrypted ID token or JARM response that wraps unsigned claims, which the library incorrectly accepted as fully validated. The relying party's public encryption key - typically published at a well-known JWKS endpoint - is all an attacker needs to forge tokens with arbitrary sub, iss, and aud values, bypassing provider signing-key possession entirely. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires three concurrent conditions: (1) the target application runs oidcc versions 3.2.0-beta.1 through before 3.9.0; (2) the OpenID Provider or relying party configuration enables encrypted ID tokens (id_token_encryption_alg_values_supported is set, e.g., to RSA-OAEP) or JARM is in use for authorization responses; and (3) the attacker can obtain the relying party's public encryption key, which in standard deployments is publicly accessible via the JWKS URI. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 score of 7.6 (AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N) captures a network-reachable, unauthenticated flaw with high confidentiality and integrity impact, tempered by two limiting factors: AT:P (specific attack prerequisites - encrypted token support must be configured) and UI:P (victim must initiate an authentication flow). … 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 oidcc to version 3.9.0 or later, which incorporates the fix committed at https://github.com/erlef/oidcc/commit/5f62fbccdae8526ff62653b8901657a6c1400fd9 and detailed in the vendor advisory at https://github.com/erlef/oidcc/security/advisories/GHSA-533g-4vf3-xwrj. … Detailed patch versions, workarounds, and compensating controls in full report. |
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