What is the CVSS score of CVE-2026-21393?

CVE-2026-21393 has a CVSS 3.0 base score of 5.4 (Medium). CVSS vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N. EPSS exploitation probability: 0.0%.

Which versions of Edit Comment. If are affected by CVE-2026-21393?

Organizations using Movable Type should be aware of moderate risk from CVE-2026-21393, a cross-site scripting vulnerability rated CVSS 5.4.

How to fix or mitigate CVE-2026-21393?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

Edit Comment. If CVE-2026-21393

MEDIUM

Cross-site Scripting (XSS) (CWE-79)

2026-02-04 vultures@jpcert.or.jp

XSS

5.4

CVSS 3.0 · NVD

Severity by source

NVD PRIMARY

5.4 MEDIUM

AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

CVE Published

Feb 04, 2026 - 07:16 nvd

MEDIUM 5.4

DescriptionCVE.org

Movable Type contains a stored cross-site scripting vulnerability in Edit Comment. If crafted input is stored by an attacker, arbitrary script may be executed on a logged-in user's web browser. Note that Movable Type 7 series and 8.4 series, which are End-of-Life (EOL), are affected by the vulnerability as well.

AnalysisAI

Stored XSS in Movable Type's Edit Comment feature allows authenticated attackers to inject malicious scripts that execute in logged-in users' browsers, affecting both current and end-of-life versions including the 7 and 8.4 series. An attacker with login credentials can craft and store malicious input that triggers arbitrary script execution when other users view or interact with comments. No patch is currently available for this medium-severity vulnerability.

Technical ContextAI

Classified as CWE-79 (Cross-site Scripting (XSS)). Movable Type contains a stored cross-site scripting vulnerability in Edit Comment. If crafted input is stored by an attacker, arbitrary script may be executed on a logged-in user's web browser. Note that Movable Type 7 series and 8.4 series, which are End-of-Life (EOL), are affected by the vulnerability as well.

Affected ProductsAI

Movable Type contains a stored cross-site scripting vulnerability in Edit Comment

RemediationAI

Monitor vendor advisories for a patch. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.