What is the CVSS score of CVE-2021-20664?

CVE-2021-20664 has a CVSS 3.1 base score of 6.1 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. EPSS exploitation probability: 0.8%.

Movable Type CVE-2021-20664

MEDIUM

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

2021-03-05 vultures@jpcert.or.jp

XSS Movable Type Movabletype Movable Type Advanced Movable Type Premium Movable Type Premium Advanced

6.1

CVSS 3.1 · NVD

View

Vulnerability Assessment

Weakness	CWE CWE-79 OWASP Top 10:2025 A05:2025 - Injection ASVS 5.0 V1 - Encoding and Sanitization Output encoding, context-aware escaping MITRE ATT&CK 2 techniques across 2 tactics: Initial Access, Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 6.1 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, user interaction required.
Exploit ScenarioDerived	A remote attacker could inject malicious scripts into web pages viewed by other users by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

No patch listed yet 0.8% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAI

Cross-site scripting vulnerability in in Asset registration screen of Movable Type 7 r.4705 and earlier (Movable Type 7 Series), Movable Type Advanced 7 r.4705 and earlier (Movable Type Advanced 7. Rated medium severity (CVSS 6.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Sanitize all user input, use Content-Security-Policy headers, encode output contextually (HTML, JS, URL). Use frameworks with built-in XSS protection.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Cross-Site Scripting (XSS) (CWE-79), which allows attackers to inject malicious scripts into web pages viewed by other users. Cross-site scripting vulnerability in in Asset registration screen of Movable Type 7 r.4705 and earlier (Movable Type 7 Series), Movable Type Advanced 7 r.4705 and earlier (Movable Type Advanced 7 Series), Movable Type 6.7.5 and earlier (Movable Type 6.7 Series), Movable Type Premium 1.39 and earlier, and Movable Type Premium Advanced 1.39 and earlier allows remote attackers to inject an arbitrary script via unspecified vectors. Affected products include: Movabletype Movable Type, Movabletype Movable Type Advanced, Movabletype Movable Type Premium, Movabletype Movable Type Premium Advanced.

Know when Movable Type gets its next vulnerability

Watch products and get an email when something new is published
Check this CVE against your own stack and servers
Exploit and PoC references, threat intelligence from 22 sources

Continue with Google Continue with GitHub

No credit card · 7-day full trial

Severity by source

NVD PRIMARY 6.1 MEDIUM

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

DescriptionNVD

Cross-site scripting vulnerability in in Asset registration screen of Movable Type 7 r.4705 and earlier (Movable Type 7 Series), Movable Type Advanced 7 r.4705 and earlier (Movable Type Advanced 7 Series), Movable Type 6.7.5 and earlier (Movable Type 6.7 Series), Movable Type Premium 1.39 and earlier, and Movable Type Premium Advanced 1.39 and earlier allows remote attackers to inject an arbitrary script via unspecified vectors.

Threat Intelligence Overview

EPSS Score

0.8%

Top 47% exploitable

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC No

EPSS 0.8%

Patch available No

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +1

CVSS: +30

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Cross-Site Scripting MEDIUM

Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.

Affected Products (CPE)NVD

cpe:2.3:a:movabletype:movable_type:*:*:*:*:*:*:*:*

cpe:2.3:a:movabletype:movable_type_advanced:*:*:*:*:*:*:*:*

cpe:2.3:a:movabletype:movable_type_premium:*:*:*:*:*:*:*:*

cpe:2.3:a:movabletype:movable_type_premium_advanced:*:*:*:*:*:*:*:*

More in Movable Type

View all

CVE-2015-1592 HIGH Act Now POC

7.5 Feb 19

Movable Type Pro, Open Source, and Advanced before 5.2.12 and Pro and Advanced 6.0.x before 6.0.7 does not properly use

CVE-2013-0209 HIGH Act Now POC

7.5 Jan 23

lib/MT/Upgrade.pm in mt-upgrade.cgi in Movable Type 4.2x and 4.3x through 4.38 does not require authentication for reque

CVE-2021-20837 CRITICAL Act Now POC

9.8 Oct 26

Movable Type 7 r.5002 and earlier (Movable Type 7 Series), Movable Type 6.8.2 and earlier (Movable Type 6 Series), Movab

CVE-2016-5742 CRITICAL Act Now

9.8 Jan 23

SQL injection vulnerability in the XML-RPC interface in Movable Type Pro and Advanced 6.x before 6.1.3 and 6.2.x before

CVE-2022-38078 CRITICAL Act Now

9.8 Aug 24

Movable Type XMLRPC API provided by Six Apart Ltd. Rated critical severity (CVSS 9.8), this vulnerability is remotely ex

CVE-2012-1503 MEDIUM This Month POC

4.3 Aug 29

Cross-site scripting (XSS) vulnerability in Six Apart (formerly Six Apart KK) Movable Type (MT) Pro 5.13 allows remote a

CVE-2026-25776 CRITICAL Act Now

9.3 Apr 08

Code injection in Movable Type CMS allows unauthenticated remote attackers to execute arbitrary Perl code with critical

CVE-2026-96408 CRITICAL Act Now

9.3 Oct 07

Unauthenticated code injection in the upgrade script shipped with Movable Type allows a remote attacker to execute an ar

CVE-2026-103668 HIGH This Week

8.8 Oct 07

Unauthenticated SQL injection in the Site Search function of Movable Type allows a remote attacker to run arbitrary SQL

CVE-2020-5577 HIGH This Week

8.8 May 14

Movable Type series (Movable Type 7 r.4606 (7.2.1) and earlier (Movable Type 7), Movable Type Advanced 7 r.4606 (7.2.1)

CVE-2020-5576 HIGH This Week

8.8 May 14

Cross-site request forgery (CSRF) vulnerability in Movable Type series (Movable Type 7 r.4606 (7.2.1) and earlier (Movab

CVE-2013-2184 HIGH This Week

7.5 Mar 27

Movable Type before 5.2.6 does not properly use the Storable::thaw function, which allows remote attackers to execute ar

Same weakness CWE-79 – Cross-site Scripting (XSS)

View all

CVE-2020-3580 MEDIUM POC

6.1

CVE-2013-7389 MEDIUM POC

4.3

CVE-2021-25299 MEDIUM POC

6.1

CVE-2014-2120 MEDIUM

6.1

CVE-2023-40000 HIGH POC

8.3

CVE-2016-8581 MEDIUM POC

6.1

CVE-2013-5223 MEDIUM POC

5.4

CVE-2025-52367 MEDIUM POC

5.4

Same technique XSS

View all

CVE-2017-9248 CRITICAL POC

9.8

CVE-2013-1710 CRITICAL POC

10.0

CVE-2024-52875 HIGH POC

8.8

References

Advisories & patches

ADVISORY https://movabletype.org/news/2021/02/mt-760-676-released.html REF https://jvn.jp/en/jp/JVN66542874/index.html

Search Externally

GitHub PoC

Exploit-DB PacketStorm Snyk Rapid7 Nuclei Templates Trickest PoC

Back