Vulnerability Description
Mastodon is a free, open-source social network server based on ActivityPub. By nature, Mastodon performs a lot of outbound requests to user-provided domains. Mastodon, however, has some protection mechanism to disallow requests to local IP addresses (unless specified in `ALLOWED_PRIVATE_ADDRESSES`) to avoid the "confused deputy" problem. The list of disallowed IP address ranges was lacking some IP address ranges that can be used to reach local IP addresses. An attacker can use an IP address in the affected ranges to make Mastodon perform HTTP requests against loopback or local network hosts, potentially allowing access to otherwise private resources and services. This is fixed in Mastodon v4.5.4, v4.4.11, v4.3.17 and v4.2.29.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Joinmastodon | Mastodon | < 4.2.29 |
Related Weaknesses (CWE)
References
- https://github.com/mastodon/mastodon/commit/0f4e8a6240b5af1f2c3f34d2793d8610c6efPatch
- https://github.com/mastodon/mastodon/commit/17022907866710a72a1b1fc0a5ce9538bad1Patch
- https://github.com/mastodon/mastodon/commit/71ae4cf2cf5138ccdda64b1b1d665849b688Patch
- https://github.com/mastodon/mastodon/security/advisories/GHSA-xfrj-c749-jxxqVendor Advisory
FAQ
What is CVE-2026-22245?
CVE-2026-22245 is a vulnerability with a CVSS score of 7.5 (HIGH). Mastodon is a free, open-source social network server based on ActivityPub. By nature, Mastodon performs a lot of outbound requests to user-provided domains. Mastodon, however, has some protection mec...
How severe is CVE-2026-22245?
CVE-2026-22245 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-22245?
Check the references section above for vendor advisories and patch information. Affected products include: Joinmastodon Mastodon.