fast-uri vulnerable to server-side request forgery via malformed IPv6 normalizationGHSA-f65p-4m7j-42xc
HIGHFix: fastify/fast-uri@3728465GHSA-f65p-4m7j-42xc is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in fast-uri. A fix is available for fast-uri — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-f65p-4m7j-42xc.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-f65p-4m7j-42xc by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 384,534 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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.
fast-urinpmDescription
fast-uri is a URI parser for Node.js. Its custom parser for bracketed IPv6 literals does not validate the complete IPv6 grammar, so invalid trailing text in an authority can be silently discarded and a malformed attacker-controlled host is turned into a different valid IPv6 destination. For example, a bracketed literal with invalid trailing characters is normalized to the unspecified address, which a Node HTTP client then connects to a local service over loopback, and other malformed literals collapse to private-range addresses. No error is set on the parsed result, so an application checking the error field cannot detect the rewrite. An application that normalizes untrusted URLs before outbound requests, redirects, proxy routing, or address-policy enforcement can be redirected to a local or private IPv6 target, giving a server-side request forgery and address-policy bypass primitive. The affected versions are 2.3.1 up to but not including 2.4.5, 3.0.0 up to but not including 3.1.6, and 4.0.0 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which validate bracketed IP literals against the full grammar and mark malformed literals as authority errors. Users should upgrade to a patched version.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | fast-uri | ≥ 2.3.1&&< 2.4.5 | 2.4.5npm install fast-uri@2.4.5 |
| 📦npm | fast-uri | ≥ 3.0.0&&< 3.1.6 | 3.1.6npm install fast-uri@3.1.6 |
| 📦npm | fast-uri | ≥ 4.0.0&&< 4.1.3 | 4.1.3npm install fast-uri@4.1.3 |
Affected Products
fast-uriopenjsfDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fast-uri, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update fast-uri to 2.4.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f65p-4m7j-42xc is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
A Server-Side Request Forgery (SSRF) flaw was found in fast-uri, a URI parser for Node.js. The parser's incomplete validation of bracketed IPv6 literals allows attackers to inject malformed authority components that are silently normalized to different valid IPv6 destinations. This could allow an attacker to bypass…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Until updates are available, restrict the processing of user-supplied URIs to trusted sources only, implement strict allowlists for destination hosts (preferably IP-based rather than hostname-based), and apply egress filtering to prevent server-initiated connections to internal networks or cloud metadata services.Source: Red Hat security advisory for GHSA-f65p-4m7j-42xc (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 10 | cockpit-image-builder-0:94.4-1.el10_2 | RHSA-2026:71543 |
| Red Hat Satellite 6.19 for RHEL 9 | foreman-0:3.18.0.14-1.el9sat | RHSA-2026:74503 |
| Cluster Observability Operator 1.5.3 | cluster-observability-operator/troubleshooting-panel-console-plugin-rhel9:1790854494 | RHSA-2026:74609 |
| multicluster engine for Kubernetes 2.11 | multicluster-engine/console-mce-rhel9:1790133081 | RHSA-2026:72848 |
| multicluster engine for Kubernetes 2.17 | multicluster-engine/console-mce-rhel9:1790135323 | RHSA-2026:72849 |
| Network Observability (NETOBSERV) 1.12.3 | network-observability/network-observability-console-plugin-pf5-rhel9:1789978780 | RHSA-2026:70593 |
| Red Hat Advanced Cluster Management for Kubernetes 2.16 | rhacm2/console-rhel9:1788880980 | RHSA-2026:67542 |
| Red Hat Advanced Cluster Management for Kubernetes 2.16 | rhacm2/console-rhel9:1788283612 | RHSA-2026:72880 |
Frequently Asked Questions
Is GHSA-f65p-4m7j-42xc in your dependencies?
Find it across npm, including transitive dependencies.