CVE-2026-49289 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in simplesamlphp/saml2. A fix is available for simplesamlphp/saml2 — see the affected versions and patch details below.
SimpleSAMLphp SAML2: Possible DoS via XPath Transform
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
CVE-2026-49289 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 377,166 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
simplesamlphp/saml2🐘simplesamlphp/saml2-legacy🐘simplesamlphp/saml2🐘simplesamlphp/saml2-legacyReal-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
The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. In 4.19.2 and 4.20.2, the library permits attacker-controlled XPath transforms while processing XML signatures in specially crafted SAML messages. XPath evaluation can consume uncontrolled processing resources, allowing a remote unauthenticated attacker to deny service to any entity relying on SimpleSAMLphp or directly on the SAML2 library. The mitigation limits the number of transforms, permits only transform algorithms identified by the SAML 2.0 Core specification, and specifically rejects XPath transforms. This issue is fixed in versions 4.19.3 and 4.20.3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | simplesamlphp/saml2 | ≥ 4.20.0&&< 4.20.3 | 4.20.3composer require simplesamlphp/saml2:^4.20.3 |
| 🐘Packagist | simplesamlphp/saml2-legacy | ≥ 4.20.0&&< 4.20.3 | 4.20.3composer require simplesamlphp/saml2-legacy:^4.20.3 |
| 🐘Packagist | simplesamlphp/saml2 | all versions | 4.19.3composer require simplesamlphp/saml2:^4.19.3 |
| 🐘Packagist | simplesamlphp/saml2-legacy | all versions | 4.19.3composer require simplesamlphp/saml2-legacy:^4.19.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for simplesamlphp/saml2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update simplesamlphp/saml2 to 4.20.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-49289 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 CVE-2026-49289 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-49289. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-49289 in your dependencies?
O3 Security finds CVE-2026-49289 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.