CVE-2025-71381
mediumpriority · track · 0EPSS 0.003 · 22 %ileEUUSEPSS · scored 2026-10-27
Hono 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.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · low–medium · 2.7–6.9
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (2)
Products and version ranges known to be affected.
advisories (1)
Vendor and ecosystem advisories describing this.
- GHSA-q7jf-gf43-6x6pHono vulnerable to Vary Header Injection leading to potential CORS Bypass2025-10-24ghsa · osvUS
### 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.
also known as (3)
Other names and identifiers for this entity.
sources
Which sources assert this record, and when.
references (6)
External citations — patches, advisories, analysis.
- https://github.com/honojs/hono/security/advisories/GHSA-q7jf-gf43-6x6pcnnvd
- https://www.vulncheck.com/advisories/hono-vary-header-injection-in-cors-middlewarecnnvd
- https://github.com/honojs/hono/security/advisories/GHSA-q7jf-gf43-6x6penisa_euvd
- https://www.vulncheck.com/advisories/hono-vary-header-injection-in-cors-middlewareenisa_euvd
- https://github.com/honojs/hono/security/advisories/GHSA-q7jf-gf43-6x6pnvd
- https://www.vulncheck.com/advisories/hono-vary-header-injection-in-cors-middlewarenvd
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