simplesamlphp/xml-security: Missing AES-GCM Authentication Tag Validation on Encrypted Nodes Allows for Unauthorized Decryption

Exploitation

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

CVSS

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

EPSS

• CVE-2026-32600: 0.15% estimated exploitation activity in the next 30 days; percentile 4.28 (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 XML nodes encrypted with either aes-128-gcm, aes-192-gcm, or aes-256-gcm lack validation of the authentication tag length. An attacker can use this to brute-force an authentication tag, recover the GHASH key, and decrypt the encrypted nodes. It also allows to forge arbitrary ciphertexts without knowing the encryption key. Details When decrypting with either aes-128-gcm, aes-192-gcm, or aes-256-gcm here, the $authTag is set from a substr(), but never has its length validated (it should be validated with something like strlen($authTag) == self::AUTHTAGLENGTH). For that reason, a shorter than expected data blob will allow for the $authTag to have as short a tag as only one byte (see PHP's documentation%20has%20been%20called.%20Otherwise%20the%20decryption%20may%20succeed%20if%20the%20given%20tag%20only%20matches%20the%20start%20of%20the%20proper%20tag.)). See this example: With a legit ciphertext in hand, this is enough to recover the GHASH key. With that key, any authenticated…

Published by the source

13 Mar 2026, 20:44 UTC

Last modified by the source

16 Mar 2026, 22:01 UTC

Source last checked

26 Oct 2026, 14:38 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-r353-4845-pr5p

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# Patch Next advisory brief: CVE-2026-32600

Advisory: simplesamlphp/xml-security: Missing AES-GCM Authentication Tag Validation on Encrypted Nodes Allows for Unauthorized Decryption
IDs: CVE-2026-32600, GHSA-r353-4845-pr5p
Record: https://patchnext.com/advisories/cve-2026-32600 (revision 1, source checked 26 Oct 2026, 14:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: simplesamlphp/xml-security 2.3.1, 1.13.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist simplesamlphp/xml-security: affected >= 2.0.0, < 2.3.1; < 1.13.9; fixed in 1.13.9, 2.3.1

## Suggested inspection (read-only)
- Packagist simplesamlphp/xml-security: 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/xml-security.
- 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-r353-4845-pr5p (GitHub-reviewed advisory GHSA-r353-4845-pr5p lists affected ranges: Packagist simplesamlphp/xml-security >=2.0.0 =0 <1.13.9)

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