Vulnerability in Joinmastodon Mastodon
CVE-2025-62605
Mastodon is a free, open-source social network server based on ActivityPub. In Mastodon version 4.4, support for verifiable quote posts with quote controls was added, but it is possible for an attacker to bypass these controls in Mastodon versions prior to 4.4.8 and 4.5.0-beta.2. Mastodon internally treats reblogs as statuses. Since they were not special-treated, an attacker could reblog any post, then quote their reblog, technically quoting themselves, but having the quote feature a preview of the post they did not get authorization for with all of the affordances that would be otherwise denied by the quote controls. This issue has been patched in versions 4.4.8 and 4.5.0-beta.2.
EPSS: 0.003 (18.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
Affected products
- Joinmastodon Mastodon — versions 4.5.0
- Mastodon — versions >= 4.4.0-beta.1, < 4.4.8, = 4.5.0-beta.1
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 (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2025-62605?
- CVE-2025-62605 is a medium-severity vulnerability in Joinmastodon Mastodon, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 4.3/10. Published 2025-10-21.
- How severe is CVE-2025-62605?
- Medium severity. CVSS v3 base score is 4.3 out of 10.