CVE-2026-42155

CRITICALNVD 9.39.3—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.3 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 81% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
9.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.3Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Magento Long Term Support (LTS) is an unofficial, community-driven project provides an alternative to the Magento Community Edition e-commerce platform with a high level of backward compatibility. Prior to 20.18.0, the XML-RPC / SOAP API session ID is generated using an outdated, time-based construction rather than a Cryptographically Secure Pseudo-Random Number Generator (CSPRNG).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. Because the resulting digest relies entirely on the timestamp and the PHP internal LCG state, the effective entropy is severely constrained. This violates the OWASP ASVS v4 requirement of ≥ 64 bits of entropy (V3.2.2) and NIST SP 800-63B standards. By narrowing the LCG window (via server state leaks or general predictability) and leveraging the lack of API rate-limiting, an attacker can generate a localized pool of candidate MD5 hashes and execute a high-speed online brute-force attack to hijack active API sessions. This vulnerability is fixed in 20.18.0.

CVSS v3
9.3
EG Score
9.3(medium)
EG Risk
73(Attend)
EG Risk 73/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity93% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
0%
EPSS %ILE
23%
KEV
Not listed

Published

May 15, 2026

Last Modified

May 18, 2026

Advisory Details (1)

Auto-updated Sep 15, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

Weak API Session ID — Predictable MD5 of Time-Derived Inputs - magento-lts · Advisory · OpenMage/magento-lts · GitHub

https://github.com/OpenMage/magento-lts/security/advisories/GHSA-2cwr-gcf9-pvxr

Vendor Advisories for CVE-2026-42155(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Packagist(1)
PackageVulnerable rangeFixed inDependents
openmage/magento-lts1.9.1.1 ... v20.9.0 (91 versions)20.18.0—

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 6× in last 7d / 28× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 156 total refreshes for this CVE.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-17 19:31 UTCEPSS rescore
  3. 2026-09-16 14:08 UTCEPSS rescore
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  7. 2026-09-11 18:10 UTCOSV refresh
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  1. 2026-08-21 23:49 UTCEPSS rescore
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  3. 2026-08-20 19:24 UTCEG score recompute
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  26. 2026-08-06 14:25 UTCEG score recompute
  27. 2026-08-06 13:46 UTCEPSS rescore
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  29. 2026-08-05 19:17 UTCEPSS rescore
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  32. 2026-08-03 18:56 UTCEG score recompute
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  44. 2026-07-25 14:18 UTCEPSS rescore
  45. 2026-07-24 14:17 UTCEPSS rescore
  46. 2026-07-23 14:18 UTCEPSS rescore
  47. 2026-07-23 03:11 UTCEG score recompute
  48. 2026-07-22 14:08 UTCEPSS rescore
  49. 2026-07-20 17:08 UTCEPSS rescore
  50. 2026-07-19 14:31 UTCEPSS rescore
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  52. 2026-07-18 10:04 UTCEPSS rescore
  53. 2026-07-18 00:59 UTCOSV refresh
  54. 2026-07-16 17:03 UTCEPSS rescore
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  73. 2026-06-29 14:06 UTCEPSS rescore
  74. 2026-06-28 14:07 UTCEPSS rescore
  75. 2026-06-28 04:56 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-42155?
CVE-2026-42155 is a critical vulnerability published on May 15, 2026. Magento Long Term Support (LTS) is an unofficial, community-driven project provides an alternative to the Magento Community Edition e-commerce platform with a high level of backward compatibility. Prior to 20.18.0, the XML-RPC / SOAP API session ID is generated using an outdated, time-based…
When was CVE-2026-42155 disclosed?
CVE-2026-42155 was first published in the National Vulnerability Database on May 15, 2026, with the most recent update on May 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42155 actively exploited?
CVE-2026-42155 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 76.7% of all scored CVEs.
What is the CVSS score of CVE-2026-42155?
CVE-2026-42155 has a CVSS v3 base score of 9.3 (NVD).
How do I remediate CVE-2026-42155?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42155, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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