CVE-2026-50131

Summary

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.

Affected Software

VendorProductVersion RangeStatus
fedify-devfedify>= 0.11.2, < 1.9.12affected
fedify-devfedify>= 1.10.0, < 1.10.11affected
fedify-devfedify>= 2.0.0, < 2.0.19affected
fedify-devfedify>= 2.1.0, < 2.1.15affected
fedify-devfedify>= 2.2.0, < 2.2.4affected
fedify-devvocab-runtime< 2.0.19affected
fedify-devvocab-runtime>= 2.1.0, < 2.1.15affected
fedify-devvocab-runtime>= 2.2.0, < 2.2.4affected

Weaknesses

  • CWE-918: CWE-918: Server-Side Request Forgery (SSRF)
  • CWE-1286: CWE-1286: Improper Validation of Syntactic Correctness of Input
  • CWE-1389: CWE-1389: Incorrect Parsing of Numbers with Different Radices

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: yes
    • Technical Impact: partial

Additional References

References