critical
9.3
CWE
79
Advisory Published
Updated

CVE-2023-36459: Mastodon vulnerable to Cross-site Scripting through oEmbed preview cards

First published: Thu Jul 06 2023(Updated: )

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.

Credit: security-advisories@github.com

Affected SoftwareAffected VersionHow to fix
Mastodon>=1.3<3.5.9
Mastodon>=4.0.0<4.0.5
Mastodon>=4.1.0<4.1.3
Mastodon=3.5.16
Mastodon=4.0.x
Mastodon=4.1.x
Mastodon=4.2.x

Remedy

https://github.com/mastodon/mastodon/commit/6d8e0fae3e96f3cf4febe03fa7fcf5b95ff761b2

Never miss a vulnerability like this again

Sign up to SecAlerts for real-time vulnerability data matched to your software, aggregated from hundreds of sources.

Read MoreStart Free Trial

Reference Links

Peer vulnerabilities

(Found alongside the following vulnerabilities)

Frequently Asked Questions

  • What is CVE-2023-36459?

    CVE-2023-36459 is a vulnerability in Mastodon, a free open-source social network server, that allows an attacker to bypass HTML sanitization and include arbitrary HTML in oEmbed preview cards.

  • What is the severity of CVE-2023-36459?

    CVE-2023-36459 has a severity level of 6.1, which is considered critical.

  • How does CVE-2023-36459 affect Mastodon?

    CVE-2023-36459 affects Mastodon versions 1.3 to 3.5.9, 4.0.0 to 4.0.5, and 4.1.0 to 4.1.3.

  • What can an attacker do with CVE-2023-36459?

    An attacker can use carefully crafted oEmbed data to bypass HTML sanitization and include arbitrary HTML in oEmbed preview cards, potentially leading to further attacks.

  • How can I fix CVE-2023-36459?

    To fix CVE-2023-36459, update Mastodon to version 3.5.9, 4.0.5, or 4.1.3 or later.

Company

Resources

Contact

SecAlerts Pty Ltd.
132 Wickham Terrace
Fortitude Valley,
QLD 4006, Australia
info@secalerts.co
By using SecAlerts services, you agree to our services end-user license agreement. This website is safeguarded by reCAPTCHA and governed by the Google Privacy Policy and Terms of Service. All names, logos, and brands of products are owned by their respective owners, and any usage of these names, logos, and brands for identification purposes only does not imply endorsement. If you possess any content that requires removal, please get in touch with us.
© 2025 SecAlerts Pty Ltd.
ABN: 70 645 966 203, ACN: 645 966 203