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HIGH severity

CVE-2026-49289 — saml2

HIGHFix: simplesamlphp/saml2@0043033

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

Also known asGHSA-5cjr-mxj5-wmrx
Published
Updated
Affected
4 pkgs
Patched
4 / 4
Exploits
None indexed
Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.8%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs56th percentile — riskier than 56% of all scored CVEsHighest risk
0.06%0.47%0.88%1.28%0.6%0.8%0.8%0.8%Sep 26Nov 26Nov 26

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

4 pkgs affected
🐘simplesamlphp/saml2🐘simplesamlphp/saml2-legacy🐘simplesamlphp/saml2🐘simplesamlphp/saml2-legacy

Real-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

4 total 4 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistsimplesamlphp/saml2≥ 4.20.0&&< 4.20.34.20.3composer require simplesamlphp/saml2:^4.20.3
🐘Packagistsimplesamlphp/saml2-legacy≥ 4.20.0&&< 4.20.34.20.3composer require simplesamlphp/saml2-legacy:^4.20.3
🐘Packagistsimplesamlphp/saml2all versions4.19.3composer require simplesamlphp/saml2:^4.19.3
🐘Packagistsimplesamlphp/saml2-legacyall versions4.19.3composer require simplesamlphp/saml2-legacy:^4.19.3

Detection & mitigation playbook

Open-source dependency

  1. Detect

    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.

  2. 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.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

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. Thi
O3 Security · Impact-Aware SCA

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CVE-2026-49289: saml2 — Fixed in 4.20.3