CVE-2026-42462
HighCVSS 7.0Exploitation Probability (EPSS)
Low risk7th percentile - higher than 7% of all known CVEs
Summary
Fedify, a TypeScript library for building federated server apps with ActivityPub, is vulnerable to an attack exploiting JSON-LD features. An attacker can restructure a JSON-LD document without changing its Linked Data Signature, allowing modification of a third-party signed activity.
Risk Assessment
The organization may receive a modified but still validly signed activity, potentially leading to data integrity breaches and social engineering attacks.
Recommendation
Immediately update Fedify to versions 1.9.11, 1.10.10, 2.0.18, 2.1.14, or 2.2.3, depending on the branch in use.
Other vulnerabilities in Fedify
See all- CVE-2026-62857High
Fedify from version 1.2.0 through affected 1.9, 1.10, 2.0, 2.1, 2.2, and 2.3 maintenance lines, in getNodeInfo(), follows an attacker-controlled links[].href value from /.well-known/nodeinfo without scheme, redirect, or private-address validation, allowing requests to loopback, link-local, cloud metadata, and private-network services and returning their response bodies. The issue is fixed in versions 1.9.13, 1.10.12, 2.0.22, 2.1.18, 2.2.7, and 2.3.2.
- CVE-2026-50131High
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.
Original NVD description (English source)
Fedify is a TypeScript library for building federated server apps powered by ActivityPub. Prior to versions 1.9.11, 1.10.10, 2.0.18, 2.1.14, and 2.2.3, an attacker can make use of JSON-LD features to restructure a JSON-LD document that would change how Fedify interprets it without changing its Linked Data Signature, allowing them to alter a third-party signed activity they have received. Versions 1.9.11, 1.10.10, 2.0.18, 2.1.14, and 2.2.3 fix the issue.