CVE-2026-39409
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk27th percentile - higher than 27% of all known CVEs
Summary
Hono prior to version 4.12.12 does not canonicalize IPv4-mapped IPv6 client addresses before applying IPv4 allow/deny rules in ipRestriction().
Risk Assessment
In environments like Node.js dual-stack, this can cause IPv4 rules to fail to match, leading to unintended authorization behavior.
Recommendation
Update Hono to version 4.12.12 or later.
Original NVD description (English source)
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, ipRestriction() does not canonicalize IPv4-mapped IPv6 client addresses (e.g. ::ffff:127.0.0.1) before applying IPv4 allow or deny rules. In environments such as Node.js dual-stack, this can cause IPv4 rules to fail to match, leading to unintended authorization behavior. This vulnerability is fixed in 4.12.12.