Vulnerability in Joinmastodon Mastodon
CVE-2025-67500
Mastodon is a free, open-source social network server based on ActivityPub. Versions 4.2.27 and prior, 4.3.0-beta.1 through 4.3.14, 4.4.0-beta.1 through 4.4.9, 4.5.0-beta.1 through 4.5.2 have discrepancies in error handling which allow checking whether a given status exists by sending a request with a non-English Accept-Language header. Using this behavior, an attacker who knows the identifier of a particular status they are not allowed to see can confirm whether this status exists or not. This cannot be used to learn the contents of the status or any other property besides its existence. This issue is fixed in versions 4.2.28, 4.3.15, 4.4.10 and 4.5.3.
EPSS: 0.002 (10.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N.
Affected products
- Joinmastodon Mastodon
- Mastodon — versions < 4.2.28, >= 4.3.0-beta.1, < 4.3.15, >= 4.4.0-beta.1, < 4.4.10
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
Frequently asked questions
- What is CVE-2025-67500?
- CVE-2025-67500 is a low-severity vulnerability in Joinmastodon Mastodon, classified under Observable Response Discrepancy. CVSS score: 3.7/10. Published 2025-12-10.
- How severe is CVE-2025-67500?
- Low severity. CVSS v3 base score is 3.7 out of 10.