CVE-2026-49454: Relyra SAML SignatureValue not cryptographically verified -> authentication bypass

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.2%, percentile 13: FIRST’s model estimates a 0.2% chance of exploitation activity in the next 30 days, higher than 13% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes relyra (Hex (Erlang/Elixir)) >= 1.0.0, < 1.2.0, fixed in 1.2.0. Check your lockfile, including transitive dependencies.

What it is

Relyra is a strict-by-default SAML 2.0 Service Provider library for Elixir and Phoenix. Versions 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. The XMLDSig trust boundary was incomplete as :publickey.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. A forged SignatureValue carrying an attacker-controlled NameID could be accepted as {:ok}. This issue has been fixed in version 1.2.0.

From the GitHub advisory

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. :publickey.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

Weakness type: CWE-287, CWE-347.

Product: relyra (Hex (Erlang/Elixir)) · Assigned by: GitHub_M · Published: 2026-06-18

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.23% probability of exploitation activity in the next 30 days; percentile 13.

Timeline

• 2026-06-18 — CVE record published by GitHub_M
• 2026-06-22 — CVE record last updated
• 2026-06-26 — GitHub-reviewed advisory GHSA-jv46-xfwm-36j7 published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-jv46-xfwm-36j7 github.com
2. CVE.org record CVE-2026-49454 cve.org
3. NVD entry CVE-2026-49454 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

Critical Hex (Erlang/Elixir) advisories · Today’s Security Digest