Auth bypass in Joinmastodon Mastodon
CVE-2025-27399
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.
Vulnerability class: Information Disclosure
EPSS: 0.003 (27.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
Affected products
- Joinmastodon Mastodon
- Mastodon — versions < 4.1.23, >= 4.2.0, < 4.2.16, >= 4.3.0, < 4.3.4
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC)
Frequently asked questions
- What is CVE-2025-27399?
- CVE-2025-27399 is a medium-severity vulnerability in Joinmastodon Mastodon, classified under Information Disclosure. CVSS score: 5.3/10. Published 2025-02-27.
- How severe is CVE-2025-27399?
- Medium severity. CVSS v3 base score is 5.3 out of 10.