Magento LTS has Weak API Session ID — Predictable MD5 of Time-Derived Inputs

Exploitation

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

CVSS 4.0

9.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-42155: 0.37% estimated exploitation activity in the next 30 days; percentile 30.49 (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.

Affected Version: OpenMage LTS ≤ 20.16.0 (confirmed on 20.16.0) Affected File: https://github.com/OpenMage/magento-lts/blob/main/app/code/core/Mage/Api/Model/Session.php – start() method Summary The XML-RPC / SOAP API session ID is generated using an outdated, time-based construction rather than a Cryptographically Secure Pseudo-Random Number Generator (CSPRNG): All inputs to the MD5 hash are time-derived and non-secure: | Input | Value | Predictability | |----------------------------|---------------------------------------------------|----------------------------------------| | time() | Unix timestamp (seconds) | Fully predictable | | uniqid('', true) prefix | sprintf('%08x%05x', $sec, $usec/10) | Highly predictable via network timing | | uniqid('', true) suffix | phpcombinedlcg() decimal float | Process-state dependent (getpid() ^ time()) | | $sessionName | null (empty) — called without arg | Constant | Because the resulting digest relies entirely on the timestamp and the PHP…

Published by the source

5 May 2026, 19:35 UTC

Last modified by the source

15 May 2026, 23:48 UTC

Source last checked

26 Oct 2026, 14:40 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2cwr-gcf9-pvxr

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# Patch Next advisory brief: CVE-2026-42155

Advisory: Magento LTS has Weak API Session ID — Predictable MD5 of Time-Derived Inputs
IDs: CVE-2026-42155, GHSA-2cwr-gcf9-pvxr
Record: https://patchnext.com/advisories/cve-2026-42155 (revision 1, source checked 26 Oct 2026, 14:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: openmage/magento-lts 20.18.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist openmage/magento-lts: affected <= 20.17.0; fixed in 20.18.0

## Suggested inspection (read-only)
- Packagist openmage/magento-lts: 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 openmage/magento-lts.
- 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-2cwr-gcf9-pvxr (GitHub-reviewed advisory GHSA-2cwr-gcf9-pvxr lists affected ranges: Packagist openmage/magento-lts >=0 <=20.17.0)

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