CVE-2023-36459

Name: CVE-2023-36459
Creator: NVD / NIST
Published: 2023-07-06T19:15:10.727+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.1/10EPSS 1.09%

Last modified Jun 17, 2026

CVE-2023-36459 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. 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. EPSS estimates a 1.09% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

6.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

1.09%

61.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Joinmastodon	Mastodon	>= 1.3, < 3.5.9
Joinmastodon	Mastodon	>= 4.0.0, < 4.0.5
Joinmastodon	Mastodon	>= 4.1.0, < 4.1.3

References

http://www.openwall.com/lists/oss-security/2023/07/06/5Mailing List
https://github.com/mastodon/mastodon/commit/6d8e0fae3e96f3cf4febe03fa7fcf5b95ff761b2Patch, Third Party Advisory
https://github.com/mastodon/mastodon/releases/tag/v3.5.9Third Party Advisory
https://github.com/mastodon/mastodon/releases/tag/v4.0.5Third Party Advisory
https://github.com/mastodon/mastodon/releases/tag/v4.1.3Third Party Advisory
https://github.com/mastodon/mastodon/security/advisories/GHSA-ccm4-vgcc-73hpThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/07/06/5Mailing List
https://github.com/mastodon/mastodon/commit/6d8e0fae3e96f3cf4febe03fa7fcf5b95ff761b2Patch, Third Party Advisory
https://github.com/mastodon/mastodon/releases/tag/v3.5.9Third Party Advisory
https://github.com/mastodon/mastodon/releases/tag/v4.0.5Third Party Advisory
https://github.com/mastodon/mastodon/releases/tag/v4.1.3Third Party Advisory
https://github.com/mastodon/mastodon/security/advisories/GHSA-ccm4-vgcc-73hpThird Party Advisory

Timeline

Published: Jul 6, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-36459?

How severe is CVE-2023-36459?

CVE-2023-36459 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 1.09% probability of exploitation in the next 30 days.

How do I fix CVE-2023-36459?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2023-36459?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST