Is CVE-2021-20837 actively exploited?

Yes. CVE-2021-20837 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, which means exploitation in the wild has been confirmed.

Can CVE-2021-20837 be exploited remotely?

The attack vector of CVE-2021-20837 has not been classified yet.

What is the CVSS score of CVE-2021-20837?

CVE-2021-20837 has not received a CVSS score yet.

HOME VULNERABILITIESCVE-2021-20837

UNKNOWNCISA KEVIN THE WILD

CVE-2021-20837

Published: April 11, 2026

EPSS:94.19%probability of exploitation in 30 daysPercentile:99.9th

Official Description

Movable Type 7 r.5002 and earlier (Movable Type 7 Series), Movable Type 6.8.2 and earlier (Movable Type 6 Series), Movable Type Advanced 7 r.5002 and earlier (Movable Type Advanced 7 Series), Movable Type Advanced 6.8.2 and earlier (Movable Type Advanced 6 Series), Movable Type Premium 1.46 and earlier, and Movable Type Premium Advanced 1.46 and earlier allow remote attackers to execute arbitrary OS commands via unspecified vectors. Note that all versions of Movable Type 4.0 or later including unsupported (End-of-Life, EOL) versions are also affected by this vulnerability.

NVD Source

Technical Analysis

CVE-2021-20837 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

CISA has added CVE-2021-20837 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.