CVE-2026-29087 is a high-severity (CVSS 7.5) CWE-863 vulnerability in @hono/node-server. A fix is available for @hono/node-server — see the affected versions and patch details below.
@hono/node-server: Authorization bypass for protected static paths via encoded slashes in Serve Static Middleware
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 CVE-2026-29087.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
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.
@hono/node-servernpmDescription
Summary
When using @hono/node-server's static file serving together with route-based middleware protections (e.g. protecting /admin/*), inconsistent URL decoding can allow protected static resources to be accessed without authorization.
In particular, paths containing encoded slashes (%2F) may be evaluated differently by routing/middleware matching versus static file path resolution, enabling a bypass where middleware does not run but the static file is still served.
Details
The routing layer and the node-server static handler normalize request paths differently. The router preserves %2F as a literal string when matching routes, while the static handler decodes %2F into / before resolving the filesystem path.
Example request:
/admin%2Fsecret.html
This may:
- fail to match middleware intended for
/admin/*, but - still be resolved by the static handler as
/admin/secret.htmlunder the configured static root.
This does not allow access outside the configured static root and is not a path traversal vulnerability.
Impact
An unauthenticated attacker could bypass route-based authorization protections for protected static resources by supplying paths containing encoded slashes.
Applications relying solely on route-based middleware to protect static subpaths under the same static root may have exposed those resources.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @hono/node-server | all versions | 1.19.10npm install @hono/node-server@1.19.10 |
Affected Products
node-serverhonoDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @hono/node-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @hono/node-server to 1.19.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-29087 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
Frequently Asked Questions
Is CVE-2026-29087 in your dependencies?
Find it across npm, including transitive dependencies.