CVE-2023-49087
Validation of SignedInfo
Description
Validation of an XML Signature requires verification that the hash value of the related XML-document (after any optional transformations and/or normalizations) matches a specific DigestValue-value, but also that the cryptografic signature on the SignedInfo-tree (the one that contains the DigestValue) verifies and matches a trusted public key. Within the simpleSAMLphp/xml-security library (https://github.com/simplesamlphp/xml-security), the hash is being validated using SignedElementTrait::validateReference, and the signature is being verified in SignedElementTrait::verifyInternal https://github.com/simplesamlphp/xml-security/blob/master/src/XML/SignedElementTrait.php:  What stands out is that the signature is being calculated over the canonical version of the SignedInfo-tree. The validateReference method, however, uses the original non-canonicalized version of SignedInfo. ### Impact If an attacker somehow (i.e. by exploiting a bug in PHP's canonicalization function) manages to manipulate the canonicalized version's DigestValue, it would be potentially be possible to forge the signature. No possibilities to exploit this were found during the investigation.
How to fix CVE-2023-49087
To remediate CVE-2023-49087, upgrade the affected package to a fixed version below.
- —upgrade to 5.0.0-alpha.13 or later
- —upgrade to 1.6.12 or later
Is CVE-2023-49087 being exploited?
Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- >= 5.0.0-alpha.12, < 5.0.0-alpha.13