CVE-2025-23221
MEDIUMCVE-2025-23221 is a medium-severity (CVSS 5.4) CWE-835 vulnerability in @fedify/fedify. O3 Security confirms whether CVE-2025-23221 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Fedify has an Infinite loop and Blind SSRF found inside the Webfinger mechanism
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
@fedify/fedifynpmDescription
Fedify is a TypeScript library for building federated server apps powered by ActivityPub and other standards. This vulnerability allows a user to maneuver the Webfinger mechanism to perform a GET request to any internal resource on any Host, Port, URL combination regardless of present security mechanisms, and forcing the victim’s server into an infinite loop causing Denial of Service. Moreover, this issue can also be maneuvered into performing a Blind SSRF attack. This vulnerability is fixed in 1.0.14, 1.1.11, 1.2.11, and 1.3.4.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @fedify/fedify | ≥ 1.0.13&&< 1.0.14 | 1.0.14 |
| 📦npm | @fedify/fedify | ≥ 1.1.10&&< 1.1.11 | 1.1.11 |
| 📦npm | @fedify/fedify | ≥ 1.2.10&&< 1.2.11 | 1.2.11 |
| 📦npm | @fedify/fedify | ≥ 1.3.3&&< 1.3.4 | 1.3.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @fedify/fedify. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @fedify/fedify to 1.0.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-23221 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-23221 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2025-23221. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-23221 in your dependencies?
O3 detects CVE-2025-23221 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.