EUVD-2026-47803Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Primary rating from Vendor (CPANSec) · only source for this CVE.
CVSS VectorVendor: CPANSec
Lifecycle Timeline
5DescriptionCVE.org
OIDC::Lite versions through 0.12.1 for Perl allow ID Token signature verification bypass via a token-controlled algorithm allowlist in verify.
When the caller does not pin an algorithm, OIDC::Lite::Model::IDToken::verify sets $self->alg($self->header->{alg}) from the token's own header and then calls decode_jwt(token, key, 1, [$self->alg]), handing JSON::WebToken an accepted-algorithm allowlist taken from the untrusted token. A token with alg=none yields ['none'], so decode_jwt returns the claims with no signature check, and a token with alg=HS256 is verified with the RP's RSA public key as the HMAC secret (RS to HS confusion).
The ID Token is the OpenID Connect authentication assertion delivered to the Relying Party. Any caller that verifies an ID Token through the unpinned load(token)->verify path, or load(token, key) with only the key pinned, accepts a forged token carrying attacker-chosen claims such as sub and is authenticated as any user. Passing an explicit algorithm so $self->alg is already set bypasses the header-derived allowlist and is not affected.
Note that the latest version uploaded to CPAN is 0.10. Later versions are available in the git repository.
AnalysisAI
ID Token signature verification bypass in OIDC::Lite Perl library through version 0.12.1 allows unauthenticated remote attackers to forge authentication tokens by controlling the algorithm allowlist used during verification. When a relying party calls the verify method without pinning a specific algorithm, the library extracts the ‘alg’ value from the attacker-controlled token header and passes it as an accepted-algorithm allowlist, enabling ‘alg=none’ (no signature check) or key‑confusion attacks (e.g., RS256 to HS256). An attacker can impersonate any user by crafting a token with arbitrary ‘sub’ claims. No active exploitation has been confirmed, and the EPSS score (0.17%) suggests low immediate threat, but the issue is critical for unpatched systems using the unpinned verification path.
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External POC / Exploit Code
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