Vulnerability in Mastodon

CVE-2026-50129

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.11, 4.4.18, and 4.3.24, a DoS can be triggered by (Uncaught Exception vulerability), due to missing exception handling in the math sanitizer. Malformed <math> nodes can result in a DoS of a whole server or targeted users services, depending on the type of action that includes the malformed nodes and the services interacting with it. This vulnerability is fixed in 4.5.11, 4.4.18, and 4.3.24.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.005 (37.4th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 37.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-50129: held from 0.005 to 0.005.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

  • Mastodon — versions >= 4.5.0-beta.1, < 4.5.11, >= 4.4.0-beta.1, < 4.4.18, < 4.3.24

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-50129?
CVE-2026-50129 is a high-severity vulnerability in Mastodon, classified under CWE-248. CVSS score: 7.5/10. Published 2026-06-24.
How severe is CVE-2026-50129?
High severity. CVSS v3 base score is 7.5 out of 10.