CVE-2026-71849: honojs hono

Vulnerability summary

CVE-2026-71849 is a low (CVSS 3.7) vulnerability in honojs hono. EPSS estimates a 0.36% chance of exploitation in the next 30 days, higher than 27.7% of scored vulnerabilities.

Timeline

1. 07-08-2026
   PublishedVulnerability first disclosed.
2. 10-08-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-200Exposure of Sensitive Information to an Unauthorized ActorThe product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.