CVE-2025-49826 is a high-severity (CVSS 7.5) CWE-444 vulnerability in next. O3 Security confirms whether CVE-2025-49826 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Next.js DoS vulnerability via cache poisoning
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
nextnpmDescription
Next.js is a React framework for building full-stack web applications. From versions 15.0.4-canary.51 to before 15.1.8, a cache poisoning bug leading to a Denial of Service (DoS) condition was found in Next.js. This issue does not impact customers hosted on Vercel. Under certain conditions, this issue may allow a HTTP 204 response to be cached for static pages, leading to the 204 response being served to all users attempting to access the page. This issue has been addressed in version 15.1.8.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | next | ≥ 15.0.4-canary.51&&< 15.1.8 | 15.1.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for next. 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 next to 15.1.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-49826 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-2025-49826 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-2025-49826. 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-2025-49826 in your dependencies?
O3 detects CVE-2025-49826 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.