CVE-2025-71381
Hono vulnerable to Vary Header Injection leading to potential CORS Bypass
Description
### 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.
How to fix CVE-2025-71381
To remediate CVE-2025-71381, upgrade the affected package to a fixed version below.
- —upgrade to 4.10.3 or later
Is CVE-2025-71381 being exploited?
Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 4.10.3
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM4.2 | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N |