Mastodon's domain blocks & rationales ignore user approval when visibility set as "users"

published 2025-02-27 20 mo ago modified 2026-09-08 2 mo ago also BIT-mastodon-2025-27399 , EUVD-2025-5447 , GHSA-94h4-fj37-c825

cvss: 5.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 29%
public exploits: 0; none known

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.

Patch / fix

fixed in 2 links 1

bitnami mastodon 4.3.4
joinmastodon mastodon 4.1.23, 4.2.16, 4.3.4

github.com/mastodon/mastodon@6b519cf commit

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 20 mo ago (2025-02-27)

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
OSV	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
bitnami	mastodon	<4.3.4	4.3.4

Affected products

mastodon mastodon

Classification

Weakness

CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
CWE-285 Improper Authorization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary