CVE-2026-42155: OpenMage Magento LTS predictable API session ID generation

CVE-2026-42155 · Severity: critical · CVSS 4 · Published 2026-05-15

OpenMage Magento LTS, an e-commerce platform, contains a vulnerability in how it generates session identifiers for its administrative APIs. Because these identifiers are created using predictable information like the current time, an attacker can guess active session IDs. If successful, an attacker could take over an administrator's session to steal customer data, modify orders, or change product pricing.

Technologies: OpenMage, openmage/magento-lts (Packagist). Vendors: OpenMage, Packagist.

Quick answers

Is CVE-2026-42155 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-42155 being exploited in the wild.
How severe is CVE-2026-42155?
Critical severity, with a CVSS score of 4, published 15 May 2026.
Which products and versions are affected?
OpenMage <= 20.17.0; openmage/magento-lts (Packagist) <= 20.17.0, ECOSYSTEM:introduced=0,fixed=20.18.0.
Is there a fix for CVE-2026-42155?
Yes. openmage/magento-lts (Packagist): upgrade to 20.18.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-42155 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-42155?
Check whether you run OpenMage or openmage/magento-lts (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • openmage/magento-lts (Packagist): upgrade to 20.18.0 or later
    composer require openmage/magento-lts:^20.18.0

Technical details

The XML-RPC, SOAP, and REST API session IDs in OpenMage LTS are generated in `Mage_Api_Model_Session::start()` using `md5(time() . uniqid('', true))`. This construction relies on predictable inputs: the Unix timestamp, a microsecond-based prefix, and a deterministic LCG float. An attacker can narrow the entropy window by observing network timing and server state. By leveraging the lack of rate limiting on API endpoints, an attacker can perform a high-speed online brute-force attack to predict and hijack active API sessions. This grants the attacker full access to API resources, including customer PII and order management. The issue is patched in version 20.18.0 by implementing `random_bytes()` for CSPRNG-based token generation.

Affected products

  • OpenMage magento-lts (OpenMage) <= 20.17.0

Identifiers

  • CVE-2026-42155
  • GHSA-2cwr-gcf9-pvxr

Timeline

  • 2026-05-04: advisory: GHSA-2cwr-gcf9-pvxr published
  • 2026-05-05: disclosed: Public disclosure of CVE-2026-42155
  • 2026-05-15: other: Advisory updated

References

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