CVE-2025-23221 is a medium-severity (CVSS 5.4) CWE-835 vulnerability in @fedify/fedify. A fix is available for @fedify/fedify — see the affected versions and patch details below.
Fedify has an Infinite loop and Blind SSRF found inside the Webfinger mechanism
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-23221.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2025-23221 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@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 | 1.0.14npm install @fedify/fedify@1.0.14 |
| 📦npm | @fedify/fedify | ≥ 1.1.10&&< 1.1.11 | 1.1.11npm install @fedify/fedify@1.1.11 |
| 📦npm | @fedify/fedify | ≥ 1.2.10&&< 1.2.11 | 1.2.11npm install @fedify/fedify@1.2.11 |
| 📦npm | @fedify/fedify | ≥ 1.3.3&&< 1.3.4 | 1.3.4npm install @fedify/fedify@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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-23221 can be triaged on real exposure rather than presence alone.
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 Security finds CVE-2025-23221 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.