CVE-2025-23221: Fedify infinite loop and blind SSRF in WebFinger mechanism

CVE-2025-23221 · Severity: low · CVSS 3.1 · Published 2025-01-21

Fedify is a TypeScript library implementing the ActivityPub protocol, which allows servers to communicate and exchange social media content. The library's WebFinger mechanism, used to resolve remote actor identities, can be exploited by an attacker to perform blind server-side request forgery (SSRF) attacks against internal resources and trigger infinite loops that cause denial of service. This could allow attackers to access internal services like localhost databases or metadata servers, or crash victim servers.

Technologies: Fedify. Vendors: Fedify.

Quick answers

Is CVE-2025-23221 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-23221 being exploited in the wild.
How severe is CVE-2025-23221?
Low severity, with a CVSS score of 3.1, published 21 January 2025.
Which products and versions are affected?
Fedify 1.0.13, 1.1.10, 1.2.10, 1.3.3.
Is there a fix for CVE-2025-23221?
A patch was published on 2025-01-20: Patches released: 1.0.14, 1.1.11, 1.2.11, 1.3.4 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2025-23221 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2025-23221?
Check whether you run Fedify at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability exists in the lookupWebFingerInternal function, which processes actor ID URLs without proper validation of the target host and port. The function extracts the protocol and server from the actor ID and constructs a WebFinger URL, then follows HTTP 3xx redirects via custom code in a while loop without limiting the number of redirects. An attacker can craft a malicious actor ID with a redirect chain that either loops indefinitely or points to internal resources (localhost, private IPs, or arbitrary internal services). The fetch request uses "redirect: manual" but still processes Location headers, bypassing protections that would normally prevent SSRF. The vulnerability affects versions 1.0.13, 1.1.10, 1.2.10, and 1.3.3; patches are available in 1.0.14, 1.1.11, 1.2.11, and 1.3.4.

Affected products

  • Fedify fedify 1.0.13, 1.1.10, 1.2.10, 1.3.3

Identifiers

  • CVE-2025-23221
  • GHSA-c59p-wq67-24wx

Timeline

  • 2025-01-21: disclosed
  • 2025-01-20: patched: Patches released: 1.0.14, 1.1.11, 1.2.11, 1.3.4

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.