CVE-2026-42155
CRITICALDescription
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 Prior to 20.18.0, the XML-RPC / SOAP API session ID is generated using an outdated, time-based construction rather than a Cryptographically Secure Pseudo-Random Number Generator (CSPRNG).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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v4 Vector
Exploitability
Impact
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Exploit Intelligence
Low risk: more likely to be exploited than 19% of all known CVEs.
References
Related Vulnerabilities
Other CWE-330 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2019-5420 | Critical | 9.8 | 92% | - | Fix |
| CVE-2021-34646 | Critical | 9.8 | 51% | - | - |
| CVE-2008-0087 | High | 7.5 | 32% | - | - |
| CVE-2017-6026 | Critical | 9.1 | 32% | - | - |
| CVE-2018-17888 | Critical | 9.8 | 27% | - | - |
| CVE-2020-11901 | Critical | 9.0 | 21% | - | Fix |
Common questions
How do I fix CVE-2026-42155?
No published fix for CVE-2026-42155 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-42155 being actively exploited?
Not that we know of. CVE-2026-42155 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.27% is the estimated probability that it will be exploited in the next 30 days. That is higher than 19% of all scored CVEs.
How severe is CVE-2026-42155?
CVE-2026-42155 has a CVSS v4 base score of 9.3, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-17.