Is CVE-2021-20815 in the CISA KEV catalog?

No. CVE-2021-20815 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-20815?

CVE-2021-20815 has a CVSS v3 base score of 6.1 (MEDIUM).

What is the EPSS score for CVE-2021-20815?

CVE-2021-20815 has an EPSS score of 0.90% (55th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-20815?

Upgrade movable type to 7.8.0 or later.

CVE & CISA-KEV Catalog

CVE-2021-20815

MEDIUM

6.1

CVSS v3

NVD

Description

Cross-site scripting vulnerability in Edit Boilerplate screen of Movable Type (Movable Type 7 r.4903 and earlier (Movable Type 7 Series), Movable Type 6.8.0 and earlier (Movable Type 6 Series), Movable Type Advanced 7 r.4903 and earlier (Movable Type Advanced 7 Series), Movable Type Premium 1.44 and earlier, and Movable Type Premium Advanced 1.44 and earlier) allows remote attackers to inject arbitrary script or HTML via unspecified vectors.

CWE-79Cross-Site Scripting (XSS)

How to fix

Remediation Available

movable typeNVD

Affected:>= 7.0, < 7.8.0Fixed in:7.8.0CVE-2021-20815derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeChanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Exploit Intelligence

0.90%probability of exploitation in 30 days

55thpercentile

Moderate risk: more likely to be exploited than 55% of all known CVEs.

References

Vendor Advisory1

movabletype.org

Third-Party Advisory1

jvn.jp

Related Vulnerabilities

Other CWE-79 (Cross-Site Scripting (XSS)) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-11022	Medium	6.9	99%	-	Fix
CVE-2019-3929	Critical	9.8	99%	KEV	Fix
CVE-2020-9496	Medium	6.1	99%	-	-
CVE-2023-28341	Medium	6.1	99%	-	Fix
CVE-2018-12998	Medium	6.1	98%	-	-
CVE-2025-4123	High	7.6	98%	-	Fix

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Markdown

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HTML

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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 2024-11-21.