CVE-2026-42462: Fedify-Dev Fedify

High severity, CVSS 7.0. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Fedify-Dev Fedify: from 2.2.0, before 2.2.3 (fixed in 2.2.3); from 2.1.0, before 2.1.14 (fixed in 2.1.14); from 2.0.0, before 2.0.18 (fixed in 2.0.18); from 1.10.0, before 1.10.10 (fixed in 1.10.10); before 1.9.11 (fixed in 1.9.11)

Published 2026-06-10. Last modified 2026-07-23.