Description
Mastodon is a free, open-source social network server based on ActivityPub. Starting in version 1.3 and prior to versions 3.5.9, 4.0.5, and 4.1.3, an attacker using carefully crafted oEmbed data can bypass the HTML sanitization performed by Mastodon and include arbitrary HTML in oEmbed preview cards. This introduces a vector for cross-site scripting (XSS) payloads that can be rendered in the user's browser when a preview card for a malicious link is clicked through. Versions 3.5.9, 4.0.5, and 4.1.3 contain a patch for this issue.
References (6)
Core 6
Core References
Third Party Advisory x_refsource_confirm
https://github.com/mastodon/mastodon/security/advisories/GHSA-ccm4-vgcc-73hp
Patch, Third Party Advisory x_refsource_misc
https://github.com/mastodon/mastodon/commit/6d8e0fae3e96f3cf4febe03fa7fcf5b95ff761b2
Third Party Advisory x_refsource_misc
https://github.com/mastodon/mastodon/releases/tag/v3.5.9
Third Party Advisory x_refsource_misc
https://github.com/mastodon/mastodon/releases/tag/v4.0.5
Third Party Advisory x_refsource_misc
https://github.com/mastodon/mastodon/releases/tag/v4.1.3
Scores
CVSS v3
9.3
EPSS
0.0019
EPSS Percentile
40.4%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
total
Details
CWE
CWE-79
Status
published
Products (1)
joinmastodon/mastodon
1.3 - 3.5.9
Published
Jul 06, 2023
Tracked Since
Feb 18, 2026