GHSA-9p8x-f768-wp2g

xml-crypto Vulnerable to XML Signature Verification Bypass via Multiple SignedInfo References

# Impact An attacker may be able to exploit this vulnerability to bypass authentication or authorization mechanisms in systems that rely on xml-crypto for verifying signed XML documents. The vulnerability allows an attacker to modify a valid signed XML message in a way that still passes signature verification checks. For example, it could be used to alter critical identity or access control attributes, enabling an attacker with a valid account to escalate privileges or impersonate another user. # Patches All versions <= 6.0.0 are affected. Please upgrade to version 6.0.1. If you are still using v2.x or v3.x please upgrade to the associated patch version. # Indicators of Compromise When logging XML payloads, check for the following indicators. If the payload includes encrypted elements, ensure you analyze the decrypted version for a complete assessment. (If encryption is not used, analyze the original XML document directly). This applies to various XML-based authentication and authorization flows, such as SAML Response payloads. ### Multiple SignedInfo Nodes There should not be more than one SignedInfo node inside a Signature. If you find multiple SignedInfo nodes, it could indicate an attack. ```xml <Signature> <SomeNode> <SignedInfo> <Reference URI="somefakereference"> <DigestValue>forgeddigestvalue</DigestValue> </Reference> </SignedInfo> </SomeNode> <SignedInfo> <Reference URI="realsignedreference"> <DigestValue>realdigestvalue</DigestValue> </Reference> </SignedInfo> </SignedInfo> </Signature> ``` ### Code to test Pass in the decrypted version of the document ```js decryptedDocument = ... // yours to implement // This check is per-Signature node, not per-document const signedInfoNodes = xpath.select(".//*[local-name(.)='SignedInfo']", signatureNode); if (signedInfoNodes.length === 0) { // Not necessarily a compromise, but invalid. Should contain exactly one SignedInfo node // Yours to implement } if (signedInfoNodes.length > 1) { // Compromise detected, yours to implement } ```