CVE-2023-49087 is a medium-severity (CVSS 6.8) CWE-345 vulnerability in simplesamlphp/xml-security. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for simplesamlphp/xml-security — see the affected versions and patch details below.
Validation of SignedInfo
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
simplesamlphp/xml-security🐘simplesamlphp/saml2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | simplesamlphp/xml-security | ≥ 1.6.11&&< 1.6.12 | 1.6.12composer require simplesamlphp/xml-security:^1.6.12 |
| 🐘Packagist | simplesamlphp/saml2 | ≥ 5.0.0-alpha.12&&< 5.0.0-alpha.13 | 5.0.0-alpha.13composer require simplesamlphp/saml2:^5.0.0-alpha.13 |
Affected Products
saml2simplesamlphpxml-securitysimplesamlphpResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for simplesamlphp/xml-security, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update simplesamlphp/xml-security to 1.6.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-49087 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2023-49087 in your dependencies?
Find it across Packagist, including transitive dependencies.