CVE-2026-62857 is a Server-Side Request Forgery (SSRF) vulnerability in the fedify TypeScript library used for building federated server apps powered by ActivityPub. Versions from 1.2.0 up to but not including 1.9.13, 1.10.12, 2.0.22, 2.1.18, 2.2.7, and 2.3.2 are affected. The vulnerability arises because the getNodeInfo() function follows attacker-controlled links[].href values from /.well-known/nodeinfo without validating the scheme, redirects, or private addresses. This allows an attacker to make requests to internal network services such as loopback, link-local, cloud metadata, and private network endpoints and receive their response bodies. The issue is fixed in the specified patched versions.
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.
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.
CVE-2026-25808 is a high-severity vulnerability in Hollo, a federated microblogging platform using ActivityPub. Versions prior to 0.6.20 and 0.7.2 improperly expose direct messages and followers-only posts via the ActivityPub outbox endpoint without requiring authorization. This results in unauthorized disclosure of private communications and restricted content. The vulnerability does not require authentication or user interaction and can be exploited remotely over the network. It affects confidentiality but not integrity or availability. The issue is fixed in versions 0.
Fedify is a TypeScript library for building federated server apps powered by ActivityPub. Prior to versions 1.6.13, 1.7.14, 1.8.15, and 1.9.2, a Regular Expression Denial of Service (ReDoS) vulnerability exists in Fedify's document loader. The HTML parsing regex at packages/fedify/src/runtime/docloader.ts:259 contains nested quantifiers that cause catastrophic backtracking when processing maliciously crafted HTML responses. This issue has been patched in versions 1.6.13, 1.7.14, 1.8.15, and 1.9.2.
Fedify is a TypeScript library for building federated server apps powered by ActivityPub. In versions below 1.3.20, 1.4.0-dev.585 through 1.4.12, 1.5.0-dev.636 through 1.5.4, 1.6.0-dev.754 through 1.6.7, 1.7.0-pr.251.885 through 1.7.8 and 1.8.0-dev.909 through 1.8.4, an authentication bypass vulnerability allows any unauthenticated attacker to impersonate any ActivityPub actor by sending forged activities signed with their own keys. Activities are processed before verifying the signing key belongs to the claimed actor, enabling complete actor impersonation across all Fedify instances. This is fixed in versions 1.3.20, 1.4.13, 1.5.5, 1.6.8, 1.7.9 and 1.8.5.
Hollo is a federated single-user microblogging software designed to be federated through ActivityPub. Versions prior to 0.6.5 allow HTML form elements to be submitted, making the software vulnerable to HTML injection. Version 0.6.5 fixes the issue.