GHSA-7p8r-x3mc-p8w7 is a high-severity (CVSS 7.5) CWE-436 vulnerability in fast-uri. A fix is available for fast-uri — see the affected versions and patch details below.
fast-uri vulnerable to host confusion via backslash authority introducer
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-7p8r-x3mc-p8w7.
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
GHSA-7p8r-x3mc-p8w7 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 374,847 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.
fast-urinpmDescription
Impact
fast-uri v4.1.1 and earlier require a literal // to recognize a URI authority, so a reference that uses \\, /\, or \/ as the authority introducer (in place of //, after an optional scheme) is parsed with no authority: the sequence and everything after it fold into the path. Node's native WHATWG URL (used by fetch(), undici, and Node's http/https clients) instead treats \ as interchangeable with / for special schemes (http, https, ws, wss, ftp, file), so the two parsers extract different hosts from the same input.
For example, fast-uri resolves \\evil.com/path against base https://allowed.com/ to https://allowed.com/%5C%5Cevil.com/path (confined to the trusted host), while Node's WHATWG URL resolves the same reference to https://evil.com/path.
Applications that use fast-uri to enforce host-based policy (allowlists, denylists, loopback/SSRF filtering, redirect validation, outbound proxy routing) before passing the same URL into Node's URL or fetch() consumers see a policy/use desync and can be steered to an unintended destination.
Patches
Upgrade to fast-uri v4.1.2, v3.1.5, v2.4.4.
Workarounds
None. Upgrade to the patched version.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | fast-uri | all versions | 2.4.4npm install fast-uri@2.4.4 |
| 📦npm | fast-uri | ≥ 3.0.0&&< 3.1.5 | 3.1.5npm install fast-uri@3.1.5 |
| 📦npm | fast-uri | ≥ 4.0.0&&< 4.1.2 | 4.1.2npm install fast-uri@4.1.2 |
Detection & 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 2.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-7p8r-x3mc-p8w7 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 GHSA-7p8r-x3mc-p8w7 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-7p8r-x3mc-p8w7. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
This is an Important host confusion vulnerability in fast-uri, which can affect Red Hat products that use the library for URI parsing and security policy enforcement. The discrepancy in how fast-uri handles backslash-based URI authority introducers compared to Node.js's native URL parser can lead to bypasses of…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Hardened Images | grafana13-1-main-13.1.1-0.4.hum1 | RHSA-2026:49387 |
| Red Hat Hardened Images | grafana12-4-main-12.4.6-0.3.hum1 | RHSA-2026:49401 |
| Red Hat OpenShift Container Platform 4.16 | openshift4/ose-monitoring-plugin-rhel9:1788235712 | RHSA-2026:62550 |
Frequently Asked Questions
Is GHSA-7p8r-x3mc-p8w7 in your dependencies?
O3 Security finds GHSA-7p8r-x3mc-p8w7 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.