CVE-2025-71381
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedHono before 4.10.2 (fixed in 4.10.3) contains a flaw in its CORS middleware: when the origin is not set to "*", the middleware copies the Vary header from the incoming request into the response. Because Vary is a response header that should be managed by the server, an attacker can supply arbitrary Vary values that are reflected into the response, potentially causing cache key pollution and inconsistent CORS enforcement in environments that rely on shared caches or proxies.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe CORS middleware in Hono before 4.10.3 reflects the Vary header from incoming requests into responses when the origin is not set to '*'. This allows attackers to inject arbitrary Vary header values, enabling cache key pollution and inconsistent CORS enforcement in environments using shared caches or proxies.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed Hono versionRun npm list hono or check your package.json to determine the installed version of the Hono packageAffected if The installed version is earlier than 4.10.3
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Identify CORS middleware usageSearch your codebase for imports or usage of the CORS middleware from Hono, such as import { cors } from 'hono/cors' or app.use('*', cors())Affected if The default CORS middleware from Hono is being used in your application
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Verify CORS origin configurationExamine the CORS middleware configuration in your code. Look for the origin parameter in the cors() options to determine how it is setAffected if The origin is NOT set to the wildcard '*' (for example, if it is set to a specific domain, array of domains, or a function that returns the request origin)
You are affected if you are using Hono version earlier than 4.10.3 with the default CORS middleware configured with an origin value other than '*', since this allows arbitrary Vary header injection from incoming requests.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade to Hono 4.10.3 or later. Alternatively, implement custom CORS handling that does not reflect client-supplied Vary headers.
4.10.3
- Check the current version of Hono in your project (package.json or package-lock.json)
- Update the Hono dependency to version 4.10.3 or later: npm install hono@^4.10.3 or yarn add hono@^4.10.3
- Run npm install or yarn install to update the package
- Verify the installed version is 4.10.3 or higher: npm list hono
- Test your application's CORS functionality to ensure it works correctly with the updated package
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.
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Free · runs locallyCheck whether your project pulls in CVE-2025-71381 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-71381 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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