What’s Vulnerable › Vulnerabilities

CVE-2023-36462: Mastodon's verified profile links can be formatted in a misleading way

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% 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-20

Description

Mastodon is a free, open-source social network server based on ActivityPub. Starting in version 2.6.0 and prior to versions 3.5.9, 4.0.5, and 4.1.3, an attacker can craft a verified profile link using specific formatting to conceal arbitrary parts of the link, enabling it to appear to link to a different URL altogether. The link is visually misleading, but clicking on it will reveal the actual link. This can still be used for phishing, though, similar to IDN homograph attacks. Versions 3.5.9, 4.0.5, and 4.1.3 contain a patch for this issue.

Affected products

• mastodon: from 2.6.0 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

• https://github.com/mastodon/mastodon/commit/610731b03dfcadd887078cb0399f4e514aa1931c
• 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-55j9-c3mp-6fcq
• https://github.com/mastodon/mastodon/commit/610731b03dfcadd887078cb0399f4e514aa1931c
• 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-55j9-c3mp-6fcq

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