Is CVE-2025-27399 in the CISA KEV catalog?

No. CVE-2025-27399 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-27399?

CVE-2025-27399 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2025-27399?

CVE-2025-27399 has an EPSS score of 0.33% (25th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2025-27399?

Upgrade mastodon to 4.3.4 or later.

CVE & CISA-KEV Catalog

CVE-2025-27399

MEDIUM

5.3

CVSS v3

NVD

Description

Mastodon is a self-hosted, federated microblogging platform. In versions prior to 4.1.23, 4.2.16, and 4.3.4, when the visibility for domain blocks/reasons is set to "users" (localized English string: "To logged-in users"), users that are not yet approved can view the block reasons. Instance admins that do not want their domain blocks to be public are impacted. Versions 4.1.23, 4.2.16, and 4.3.4 fix the issue.

CWE-200Information Exposure CWE-285

How to fix

Remediation Available

mastodonNVD

Affected:>= 4.3.0, < 4.3.4Fixed in:4.3.4CVE-2025-27399derived 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 InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

0.33%probability of exploitation in 30 days

25thpercentile

Low risk: more likely to be exploited than 25% of all known CVEs.

References

Patch1

github.com

Vendor Advisory1

github.com

Product2

Related Vulnerabilities

Other CWE-200 (Information Exposure) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-24919	High	8.6	100%	KEV + Ransom	-
CVE-2020-14181	Medium	5.3	100%	-	Fix
CVE-2021-34429	Medium	5.3	99%	-	Fix
CVE-2018-11409	Medium	5.3	98%	-	-
CVE-2021-41277	Critical	10.0	97%	KEV	-
CVE-2016-2183	High	7.5	96%	-	Fix

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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 2025-06-24.