CVE-2025-71381 — hono
Fix: honojs/hono@d9b8b4bCVE-2025-71381 is a CWE-113 vulnerability in hono. A fix is available for hono — see the affected versions and patch details below.
Hono - Vary Header Injection in CORS 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-2025-71381.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
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.
hononpmDescription
Summary
A flaw in the CORS middleware allowed request Vary headers to be reflected into the response, enabling attacker-controlled Vary values and potentially affecting cache behavior.
Details
The middleware previously copied the Vary header from the request when origin was not set to "*". Since Vary is a response header that should only be managed by the server, this could allow an attacker to influence caching behavior or cause inconsistent CORS handling.
Most environments will see impact only when shared caches or proxies rely on the Vary header. The practical effect varies by configuration.
Impact
May cause cache key pollution and inconsistent CORS enforcement in certain setups. No direct confidentiality, integrity, or availability impact in default configurations.
Resolution
Update to the latest patched release. The CORS middleware has been corrected to handle Vary exclusively as a response header.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | hono | all versions | 4.10.3npm install hono@4.10.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update hono to 4.10.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-71381 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.
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.
Red Hat products that include the Hono npm package already ship version 4.11.4 or later, which contains the fix for this vulnerability. No Red Hat products are affected.
No mitigation is needed. All Red Hat products shipping the Hono npm package already include a version that contains the fix for this issue.Source: Red Hat security advisory for CVE-2025-71381 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2025-71381 in your dependencies?
Find it across npm, including transitive dependencies.