Mastodon: Persistent anonymous DoS via unhandled NoMethodError in MATH_TRANSFORMER

published 2026-06-24 4 mo ago modified 2026-07-08 4 mo ago also BIT-mastodon-2026-50129 , EUVD-2026-39060 , GHSA-qrgq-9fx2-vf2r

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits: 0; none known

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.

Patch / fix

fixed in 2

bitnami mastodon 4.3.24, 4.4.18, 4.5.11
joinmastodon mastodon 4.3.24, 4.4.18, 4.5.11

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 4 mo ago (2026-06-25)

Exploit prediction

0.46% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem	package	affected	fixed in
bitnami	mastodon	<4.3.24 >=4.4.0, <4.4.18 >=4.5.0, <4.5.11	4.3.24 4.4.18 4.5.11

Affected products

mastodon mastodon

Classification

Weakness

CWE-248 Uncaught Exception

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