Description

passport-saml-encrypted through 0.1.13 makes SAML signature verification conditional on an optional cert option, allowing attackers to bypass authentication by submitting unsigned SAML responses. Attackers can post forged SAML responses with arbitrary NameID and attributes to the assertion consumer service endpoint to receive authenticated profiles without valid signatures.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.1",
  "pubDate": "2026-09-10T18:18:15.910Z",
  "pubdate": "2026-09-10T18:18:15.910Z",
  "executiveSummary": "The passport-saml-encrypted package through version 0.1.13 is vulnerable to a critical authentication bypass vulnerability due to insecure cryptographic signature verification. The implementation makes the validation of SAML signatures conditional on the presence of an optional cert configuration option. When this option is omitted or not strictly enforced, the library defaults to allowing unsigned assertions.\nThis flaw enables remote, unauthenticated attackers to completely bypass the authentication layer of applications utilizing this library. An attacker can construct a forged SAML response containing an arbitrary NameID and custom user attributes and submit it directly to the application's assertion consumer service endpoint. Because signature verification is bypassed, the application will trust the spoofed identity claims, granting the attacker authenticated access to the target profile without requiring a valid cryptographic signature or legitimate credentials.",
  "technicalDetails": "The core vulnerability in passport-saml-encrypted (up to and including version 0.1.13) lies within its SAML assertion parsing logic. In a secure SAML service provider flow, incoming XML assertions must be cryptographically validated against a trusted public key certificate to ensure they have not been tampered with and indeed originated from the trusted Identity Provider (IdP). However, the library's verification function evaluates the cryptographic signature only if the cert configuration parameter is defined and actively passed to the validation routine.\nIf the library is instantiated or configured in a manner where the cert property is missing, null, or undefined, the verification code conditionally skips the signature validation block entirely. Rather than throwing an error or rejecting the unsigned payload, the library proceeds to parse the XML document as if it were a valid, verified assertion.\nThe step-by-step attack flow proceeds as follows:\n1. The attacker targets an application running passport-saml-encrypted (<= 0.1.13) and identifies its assertion consumer service endpoint, which handles incoming SAML responses.\n2. The attacker crafts a malicious SAML Response payload. This payload contains forged assertion elements, including a customized NameID specifying a target victim (such as an administrator) and administrative attributes, but completely lacks a valid cryptographic signature.\n3. The attacker encodes this forged XML payload (typically using Base64 encoding) and transmits it via an HTTP POST request to the assertion consumer service endpoint.\n4. The vulnerable middleware receives the request. Due to the conditional validation flaw, the library bypasses signature verification routines because of the absent or unforced cert check.\n5. The library extracts the identity claims from the forged NameID and constructs an authenticated user profile.\n6. The application establishes an authenticated session, granting the attacker full unauthorized access under the assumed identity.\nThis vulnerability requires no previous authentication or special privileges to exploit, is fully exploitable over the network, and results in complete compromise of the application's authentication and authorization model."
}