CVE-2023-42450: Mastodon is a free, open-source social network server based on ActivityPub. Starting in version 4.2.0-beta1 and prior to version 4.2.0-rc2, by craftin...

Description

Mastodon is a free, open-source social network server based on ActivityPub. Starting in version 4.2.0-beta1 and prior to version 4.2.0-rc2, by crafting specific input, attackers can inject arbitrary data into HTTP requests issued by Mastodon. This can be used to perform confused deputy attacks if the server configuration includes `ALLOWED_PRIVATE_ADDRESSES` to allow access to local exploitable services. Version 4.2.0-rc2 has a patch for the issue.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

0.39%

30.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions	Update
Joinmastodon	Mastodon	4.2.0	Beta1

References

Timeline

Published: Sep 19, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-42450?

Mastodon is a free, open-source social network server based on ActivityPub. Starting in version 4.2.0-beta1 and prior to version 4.2.0-rc2, by crafting specific input, attackers can inject arbitrary data into HTTP requests issued by Mastodon. This can be used to perform confused deputy attacks if the server configuration includes `ALLOWED_PRIVATE_ADDRESSES` to allow access to local exploitable services. Version 4.2.0-rc2 has a patch for the issue.

How severe is CVE-2023-42450?

CVE-2023-42450 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.39% probability of exploitation in the next 30 days.

How do I fix CVE-2023-42450?

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.