xml-crypto is an xml digital signature and encryption library for Node.js. In affected versions the default configuration does not check authorization of the signer, it only checks the validity of the signature per section 3.2.2 of the w3 xmldsig-core-20080610 spec. As such, without additional validation steps, the default configuration allows a malicious actor to re-sign an XML document, place the certificate in a `<KeyInfo />` element, and pass `xml-crypto` default validation checks. As a result `xml-crypto` trusts by default any certificate provided via digitally signed XML document's `<KeyInfo />`. `xml-crypto` prefers to use any certificate provided via digitally signed XML document's `<KeyInfo />` even if library was configured to use specific certificate (`publicCert`) for signature verification purposes. An attacker can spoof signature verification by modifying XML document and replacing existing signature with signature generated with malicious private key (created by attacker) and by attaching that private key's certificate to `<KeyInfo />` element. This vulnerability is combination of changes introduced to `4.0.0` on pull request 301 / commit `c2b83f98` and has been addressed in version 6.0.0 with pull request 445 / commit `21201723d`. Users are advised to upgrade. Users unable to upgrade may either check the certificate extracted via `getCertFromKeyInfo` against trusted certificates before accepting the results of the validation or set `xml-crypto's getCertFromKeyInfo` to `() => undefined` forcing `xml-crypto` to use an explicitly configured `publicCert` or `privateKey` for signature verification.
The default configuration of xml-crypto verifies only the correctness of the signature according to the W3C xmldsig-core specification, but does not check the authorization of the signer. An attacker can modify an XML document, generate their own key pair, sign the modified document with their private key, and then place the corresponding certificate in the `<KeyInfo />` element. The library prefers the certificate contained in `<KeyInfo />` even when it has been configured to use a specific certificate (`publicCert`). As a result, signature verification succeeds, even though the document comes from an unauthorized entity.
An attacker can effectively forge XML digital signature verification, which in practice means the ability to impersonate trusted parties and deliver unauthorized, modified data as verified — with high impact on the confidentiality and integrity of processed information.
The xml-crypto library should be updated to version 6.0.0 or later. If updating is not possible, it is recommended to verify the certificate returned by `getCertFromKeyInfo` against a list of trusted certificates before accepting validation results, or set the `getCertFromKeyInfo` function to `() => undefined`, which will enforce the use of an explicitly configured `publicCert` or `privateKey`.
The xml-crypto library for Node.js in versions from 4.0.0 to earlier than 6.0.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N