Vulnerability Description
Fedify is a TypeScript library for building federated server apps powered by ActivityPub. Fedify previously addressed SSRF/internal network access in GHSA-p9cg-vqcc-grcx by adding public URL validation before runtime document and media fetching. However, the IPv4 validation logic present starting in version 0.11.2 and prior to versions 1.9.12, 1.10.11, 2.0.19, 2.1.15, and 2.2.4 appears incomplete. The `validatePublicUrl()` protection relies on `isValidPublicIPv4Address()` to reject non-public IPv4 destinations. The function blocks common private and local ranges such as `10.0.0.0/8`, `127.0.0.0/8`, `169.254.0.0/16`, `172.16.0.0/12`, and `192.168.0.0/16`, but it still treats several special-use, reserved, multicast, benchmarking, and carrier-grade NAT IPv4 ranges as valid public destinations. Because this validation is used as an SSRF defense before outbound fetches, this appears to be an incomplete mitigation or bypass class for the previous SSRF issue. Versions 1.9.12, 1.10.11, 2.0.19, 2.1.15, and 2.2.4 contain an updated patch.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/fedify-dev/fedify/security/advisories/GHSA-xw9q-2mv6-9fr8
- https://github.com/fedify-dev/fedify/security/advisories/GHSA-xw9q-2mv6-9fr8
FAQ
What is CVE-2026-50131?
CVE-2026-50131 is a vulnerability with a CVSS score of 8.6 (HIGH). Fedify is a TypeScript library for building federated server apps powered by ActivityPub. Fedify previously addressed SSRF/internal network access in GHSA-p9cg-vqcc-grcx by adding public URL validatio...
How severe is CVE-2026-50131?
CVE-2026-50131 has been rated HIGH with a CVSS base score of 8.6/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-50131?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.