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TI-2021-04052 Aliases CVE-2021-20837GHSA-fq4q-8q83-6gj7

OS command injection in Six Apart Ltd. Movable Type

Priority HIGH 84CWE-78Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
No fix listed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-78.

Summary

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.

Why it matters now

EPSS 0.88144 99th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix No fix listed No fixed version in the sources yet

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
Six Apart Ltd.Movable TypeMovable 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—No fix listedCNA
  • Movable Type VendorSix Apart Ltd. Affected 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 Fixed in — No fix listed CNA

CPE configurations NVD · 7

CPEVersionsRoleVendor
cpe:2.3:a:sixapart:movable_type:*:*:*:*:premium:*:*:*up to 1.46VulnerableSixapart
cpe:2.3:a:sixapart:movable_type:*:*:*:*:premium_advanced:*:*:*up to 1.46VulnerableSixapart
cpe:2.3:a:sixapart:movable_type:*:*:*:*:*:*:*:*4.0 – 6.3.11VulnerableSixapart
cpe:2.3:a:sixapart:movable_type:*:*:*:*:-:*:*:*6.5.0 – 6.8.2VulnerableSixapart
cpe:2.3:a:sixapart:movable_type:*:*:*:*:advanced:*:*:*6.5.0 – 6.8.2VulnerableSixapart
cpe:2.3:a:sixapart:movable_type:*:*:*:*:-:*:*:*7.0 – 7.8.1VulnerableSixapart
cpe:2.3:a:sixapart:movable_type:*:*:*:*:advanced:*:*:*7.0 – 7.8.1VulnerableSixapart
  • cpe:2.3:a:sixapart:movable_type:*:*:*:*:premium:*:*:* Versions up to 1.46 Vulnerable ·Sixapart
  • cpe:2.3:a:sixapart:movable_type:*:*:*:*:premium_advanced:*:*:* Versions up to 1.46 Vulnerable ·Sixapart
  • cpe:2.3:a:sixapart:movable_type:*:*:*:*:*:*:*:* Versions 4.0 – 6.3.11 Vulnerable ·Sixapart
  • cpe:2.3:a:sixapart:movable_type:*:*:*:*:-:*:*:* Versions 6.5.0 – 6.8.2 Vulnerable ·Sixapart
  • cpe:2.3:a:sixapart:movable_type:*:*:*:*:advanced:*:*:* Versions 6.5.0 – 6.8.2 Vulnerable ·Sixapart
  • cpe:2.3:a:sixapart:movable_type:*:*:*:*:-:*:*:* Versions 7.0 – 7.8.1 Vulnerable ·Sixapart
  • cpe:2.3:a:sixapart:movable_type:*:*:*:*:advanced:*:*:* Versions 7.0 – 7.8.1 Vulnerable ·Sixapart

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-20837
  2. 2026-10-03 Alias added: GHSA-fq4q-8q83-6gj7

References

Exploit 1

Advisory 3

  • TI-2026-20843 Code injection in Six Apart Ltd. Movable Type CVSS 4.0CRITICAL 9.3
  • TI-2026-69104 Code injection in Movable Type upgrade script CVSS 4.0CRITICAL 9.3
  • TI-2022-17791 Code injection in Six Apart Ltd. Movable Type XMLRPC API CVSS 3.1CRITICAL 9.8
  • TI-2026-69105 SQL injection in Movable Type Site Search function CVSS 4.0HIGH 8.8
  • TI-2020-04547 Unrestricted file upload in Six Apart Ltd. Movable Type CVSS 3.1HIGH 8.8
  • TI-2020-04546 Cross-site request forgery in Six Apart Ltd. Movable Type CVSS 3.1HIGH 8.8
See all 53 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences