CVE-2026-29045
HIGHCVE-2026-29045 is a high-severity (CVSS 7.5) CWE-177 vulnerability in hono. O3 Security confirms whether CVE-2026-29045 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Hono: Arbitrary file access via serveStatic vulnerability
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
hononpmDescription
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to version 4.12.4, when using serveStatic together with route-based middleware protections (e.g. app.use('/admin/*', ...)), inconsistent URL decoding allowed protected static resources to be accessed without authorization. The router used decodeURI, while serveStatic used decodeURIComponent. This mismatch allowed paths containing encoded slashes (%2F) to bypass middleware protections while still resolving to the intended filesystem path. This issue has been patched in version 4.12.4.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | hono | all versions | 4.12.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono. 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 hono to 4.12.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-29045 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-2026-29045 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-2026-29045. 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-2026-29045 in your dependencies?
O3 detects CVE-2026-29045 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.