SimpleSAMLphp has Possible DoS via XPath Transform

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-49289: 0.78% estimated exploitation activity in the next 30 days; percentile 56.10 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary This library turned out to be vulnerable to Denial-of-Service attacks using XPath transforms. A mitigation has been put in place to restrict the number of transforms and to restrict transforms to only the transform-algorithms mentioned in the SAML 2.0 Core Specifications (and specifically refuse XPath transforms). Impact An attacker is able to send specially crafted messages to any entity relying on SimpleSAMLphp (or directly on this SAML2-library) to be able to perform a Denial-of-Service attack.

Published by the source

2 Jul 2026, 20:27 UTC

Last modified by the source

5 Aug 2026, 12:44 UTC

Source last checked

26 Oct 2026, 14:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5cjr-mxj5-wmrx

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# Patch Next advisory brief: CVE-2026-49289

Advisory: SimpleSAMLphp has Possible DoS via XPath Transform
IDs: CVE-2026-49289, GHSA-5cjr-mxj5-wmrx
Record: https://patchnext.com/advisories/cve-2026-49289 (revision 1, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: simplesamlphp/saml2-legacy 4.20.3, 4.19.3; simplesamlphp/saml2 4.20.3, 4.19.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist simplesamlphp/saml2-legacy: affected >= 4.20.0, <= 4.20.2; <= 4.19.2; fixed in 4.20.3, 4.19.3
- Packagist simplesamlphp/saml2: affected >= 4.20.0, <= 4.20.2; <= 4.19.2; fixed in 4.20.3, 4.19.3

## Suggested inspection (read-only)
- Packagist simplesamlphp/saml2-legacy: check the installed version with your package manager.
- Packagist simplesamlphp/saml2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on simplesamlphp/saml2-legacy, simplesamlphp/saml2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5cjr-mxj5-wmrx (GitHub-reviewed advisory GHSA-5cjr-mxj5-wmrx lists affected ranges: Packagist simplesamlphp/saml2 >=4.20.0 =0 =4.20.0 =0 <=4.19.2)

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