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Relyra SAML SignatureValue not cryptographically verified -> authentication bypass

Critical
szTheory published GHSA-jv46-xfwm-36j7 May 25, 2026

Package

erlang relyra (Erlang)

Affected versions

>= 1.0.0, < 1.2.0

Patched versions

1.2.0

Description

Summary

Relyra 1.0.0 and 1.1.0 accept forged SAML signatures because SignatureValue was not cryptographically verified before the library returned a successful authentication result.

Details

In 1.0.0 and 1.1.0, the XMLDSig trust boundary was incomplete. :public_key.verify over the exclusive-C14N canonicalized SignedInfo was not performed against the configured IdP certificate's public key, DigestValue was not recomputed over the canonicalized referenced element, and canonicalize/2 remained an unused passthrough in the signature-verification path. The result was a structure-only acceptance path where document shape and trust-source rejection could succeed without proving the signature bytes.

Impact

A forged SignatureValue carrying an attacker-controlled NameID can be accepted as {:ok}. Any relying-party application using Relyra 1.0.0 or 1.1.0 can be logged into as an arbitrary user if it trusts the affected response path.

Patches

Relyra 1.2.0 closes the gap with real exclusive-C14N canonicalization, :public_key.verify against the configured IdP certificate's public key, and a constant-time DigestValue recompute/compare bound to the exact consumed node on both verify/4 and verify_metadata_root/4.

Workarounds

There is no safe configuration of 1.0.0 or 1.1.0. Upgrade to 1.2.0 or later.

References

  • Fix commit 2e45689 (wire real XMLDSig crypto into the candidate arm)
  • Fix commit 8910200 (close metadata trust bypass, pin over DER)
  • Regression proof: test/security/xml/adversarial_crypto_test.exs, test/relyra/metadata/auto_refresh_test.exs, test/security/ci_gate_integrity_test.exs

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVE ID

CVE-2026-49454

Weaknesses

Improper Authentication

When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Learn more on MITRE.

Improper Verification of Cryptographic Signature

The product does not verify, or incorrectly verifies, the cryptographic signature for data. Learn more on MITRE.