What’s Vulnerable › Vulnerabilities

CVE-2024-37903: Mastodon has improper authorship check on audience extension for existing posts

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2024-07-05 · updated 2026-06-17
• Weakness: CWE-862

Description

Mastodon is a self-hosted, federated microblogging platform. Starting in version 2.6.0 and prior to versions 4.1.18 and 4.2.10, by crafting specific activities, an attacker can extend the audience of a post they do not own to other Mastodon users on a target server, thus gaining access to the contents of a post not intended for them. Versions 4.1.18 and 4.2.10 contain a patch for this issue.

Affected products

• mastodon: from 2.6.0 before 4.1.18; from 4.2.0 before 4.2.10 — fixed in 4.1.18, 4.2.10

How to fix

Upgrade to a fixed version: mastodon 4.1.18, 4.2.10. Check the vendor advisory for mitigations.

References

• https://github.com/mastodon/mastodon/commit/a1c7aae28aecf06659c5b18cfa131b37cd1512a3
• https://github.com/mastodon/mastodon/commit/d4bf22b632ea8b1174375c4966a6768ab66393b6
• https://github.com/mastodon/mastodon/releases/tag/v4.1.18
• https://github.com/mastodon/mastodon/releases/tag/v4.2.10
• https://github.com/mastodon/mastodon/security/advisories/GHSA-xjvf-fm67-4qc3
• https://github.com/mastodon/mastodon/commit/a1c7aae28aecf06659c5b18cfa131b37cd1512a3
• https://github.com/mastodon/mastodon/commit/d4bf22b632ea8b1174375c4966a6768ab66393b6
• https://github.com/mastodon/mastodon/releases/tag/v4.1.18
• https://github.com/mastodon/mastodon/releases/tag/v4.2.10
• https://github.com/mastodon/mastodon/security/advisories/GHSA-xjvf-fm67-4qc3

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