Information disclosure in Honojs Hono
CVE-2026-71849
Hono is a Web application framework that provides support for any JavaScript runtime. From 4.7.0 to 4.12.33, the Proxy Helper proxy() function in hono/proxy does not remove response headers named by the origin's Connection header. Per RFC 9110 Section 7.6.1, an intermediary must remove the header fields listed in a message's Connection header field before forwarding the message, in addition to the well known hop by hop headers, but the proxy() function only removed the well known hop by hop headers, including Connection itself, from origin responses. A client may therefore receive response headers that the origin intended only for its immediate peer, disclosing connection scoped or internal metadata contained in such headers, when an application proxies responses from an origin that declares additional, non standard headers as hop by hop via the Connection response header. This issue is fixed in version 4.12.34.
Vulnerability class: Information Disclosure
Published · last modified .
CVSS v3 metric
CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.004 (29.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 29.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Honojs Hono — versions >= 4.7.0, < 4.12.34
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-71849?
- CVE-2026-71849 is a low-severity vulnerability in Honojs Hono, classified under Information Disclosure. CVSS score: 3.7/10. Published 2026-08-07.
- How severe is CVE-2026-71849?
- Low severity. CVSS v3 base score is 3.7 out of 10.