GHSA-c4cc-x928-vjw9 is a medium-severity (CVSS 6) CWE-248 vulnerability in robrichards/xmlseclibs. A fix is available for robrichards/xmlseclibs — see the affected versions and patch details below.
robrichards/xmlseclibs has an Libxml2 Canonicalization error which can bypass Digest/Signature validation
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-c4cc-x928-vjw9.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-c4cc-x928-vjw9 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
robrichards/xmlseclibsReal-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
Summary
An authentication bypass vulnerability exists due to a flaw in the libxml2 canonicalization process, which is used by xmlseclibs during document transformation. This weakness allows an attacker to generate a valid signature once and reuse it indefinitely. In practice, a signature created during a previous interaction - or through a misconfigured authentication flow - can be replayed to bypass authentication checks.
Details
When libxml2’s canonicalization is invoked on an invalid XML input, it may return an empty string rather than a canonicalized node. xmlseclibs then proceeds to compute the DigestValue over this empty string, treating it as if canonicalization succeeded.
Impact
Digest bypass: By crafting input that causes canonicalization to yield an empty string, the attacker can manipulate validation to pass incorrectly.
Signature replay on empty canonical form: If an empty string has been signed once (e.g., in a prior interaction or via a misconfigured flow), that signature can potentially be replayed to bypass authentication.
Suggested remediation
Treat canonicalization failures (exceptions or nil/empty outputs) as fatal and abort validation. Add explicit checks: reject when canonicalize returns nil/empty or raise
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | robrichards/xmlseclibs | all versions | 3.1.4composer require robrichards/xmlseclibs:^3.1.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for robrichards/xmlseclibs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update robrichards/xmlseclibs to 3.1.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c4cc-x928-vjw9 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-c4cc-x928-vjw9 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-c4cc-x928-vjw9. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-c4cc-x928-vjw9 in your dependencies?
O3 Security finds GHSA-c4cc-x928-vjw9 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.