What’s Vulnerable › Vulnerabilities
CVE-2023-36461: Mastodon vulnerable to Denial of Service through slow HTTP responses
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 1.3% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2023-07-06 · updated 2026-06-17
- Weakness: CWE-770
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.
Affected products
- mastodon: before 3.5.9; from 4.0.0 before 4.0.5; from 4.1.0 before 4.1.3 — fixed in 3.5.9, 4.0.5, 4.1.3
How to fix
Upgrade to a fixed version: mastodon 3.5.9, 4.0.5, 4.1.3. Check the vendor advisory for mitigations.
References
- http://www.openwall.com/lists/oss-security/2023/07/06/7
- 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
- https://github.com/mastodon/mastodon/security/advisories/GHSA-9pxv-6qvf-pjwc
- http://www.openwall.com/lists/oss-security/2023/07/06/7
- 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
- https://github.com/mastodon/mastodon/security/advisories/GHSA-9pxv-6qvf-pjwc
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