Incorrect signature verification in SimpleSAMLphp

Exploitation

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

CVSS

6.3 · CVSS:3.0/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:H

EPSS

• CVE-2016-9955: 1.18% estimated exploitation activity in the next 30 days; percentile 67.79 (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.

Background An incorrect check of return values in the signature validation utilities allows an attacker to get invalid signatures accepted as valid by forcing an error during validation. Description The SimpleSAMLXMLValidator class allows the verification of the XML digital signature of a SAML 1 message with a given key. In particular, the constructor of the class receives an XML node and a key to verify it and throws an exception in case there is an error, either caused by incorrect input or an invalid signature. This method uses the verify() method from the RobRichards\XMLSecDSig class to verify the signature with the given key, which in turn will end up calling opensslverify() depending on the signature algorithm used. The opensslverify() function returns 1 when the signature was successfully verified, 0 if it failed to verify with the given key and -1 in case an error occurs. PHP allows translating numerical values to boolean implicitly, with the following correspondences: - 0…

Published by the source

24 Jan 2020, 21:27 UTC

Last modified by the source

7 Feb 2024, 18:42 UTC

Source last checked

26 Oct 2026, 14:15 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-p9cm-r7jg-8q3g

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# Patch Next advisory brief: CVE-2016-9955

Advisory: Incorrect signature verification in SimpleSAMLphp
IDs: CVE-2016-9955, GHSA-p9cm-r7jg-8q3g
Record: https://patchnext.com/advisories/cve-2016-9955 (revision 1, source checked 26 Oct 2026, 14:15 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: simplesamlphp/simplesamlphp 1.14.11. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist simplesamlphp/simplesamlphp: affected < 1.14.11; fixed in 1.14.11

## Suggested inspection (read-only)
- Packagist simplesamlphp/simplesamlphp: 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/simplesamlphp.
- 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-p9cm-r7jg-8q3g (GitHub-reviewed advisory GHSA-p9cm-r7jg-8q3g lists affected ranges: Packagist simplesamlphp/simplesamlphp >=0 <1.14.11)

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