Vulnerability in Hono
CVE-2025-71381
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (19.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 20th percentile — 19.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Hono — versions 0, 4.10.2
Weakness classification (CWE)
References
- github.com/honojs/hono/security/advisories/GHSA-q7jf-gf43-6x6p (vendor-advisory)
- www.vulncheck.com/advisories/hono-vary-header-injection-in-cors-middleware (third-party-advisory)
Frequently asked questions
- What is CVE-2025-71381?
- CVE-2025-71381 is a medium-severity vulnerability in Hono, classified under HTTP Response Splitting. CVSS score: 6.5/10. Published 2026-06-30.
- How severe is CVE-2025-71381?
- Medium severity. CVSS v3 base score is 6.5 out of 10.