GHSA-ffhc-5mcf-pf4q — next
MEDIUMGHSA-ffhc-5mcf-pf4q is a medium-severity (CVSS 4.7) Cross-site Scripting (XSS) vulnerability in next. A fix is available for next — see the affected versions and patch details below.
Next.js vulnerable to cross-site scripting in App Router applications using CSP nonces
Exploitation Status
No confirmed exploitation observed yet
- 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-ffhc-5mcf-pf4q.
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-ffhc-5mcf-pf4q 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 378,567 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.
nextnpmDescription
Impact
App Router applications that rely on CSP nonces can be vulnerable to stored cross-site scripting when deployed behind shared caches. In affected versions, malformed nonce values derived from request headers could be reflected into rendered HTML in an unsafe way, allowing an attacker to poison cached responses and cause script execution for later visitors.
Fix
We now reject or ignore malformed nonce values before they are embedded into HTML and apply stricter nonce sanitization so request-derived nonce data cannot break out of the intended attribute context.
Workarounds
If you cannot upgrade immediately, strip inbound Content-Security-Policy request headers from untrusted traffic.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | next | ≥ 13.4.0&&< 15.5.16 | 15.5.16npm install next@15.5.16 |
| 📦npm | next | ≥ 16.0.0&&< 16.2.5 | 16.2.5npm install next@16.2.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for next, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update next to 15.5.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-ffhc-5mcf-pf4q 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-ffhc-5mcf-pf4q can be triaged on real exposure rather than presence alone.
Tailored to GHSA-ffhc-5mcf-pf4q. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-ffhc-5mcf-pf4q in your dependencies?
O3 Security finds GHSA-ffhc-5mcf-pf4q across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.