VulnerabilityDeferred

CVE-2026-50131

Fedify previously addressed SSRF/internal network access in GHSA-p9cg-vqcc-grcx by adding public URL validation before runtime document and media fetching.

HIGH 8.6EPSS 0.35%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.35%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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 3.1: 8.6 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
EPSS: 0.35% probability · 28th percentile
CISA KEV: Not listed
Weakness: CWE-918, CWE-1286, CWE-1389
Source: security-advisories@github.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.