CVE-2026-39409: Hono has incorrect IP matching in ipRestriction() for IPv4-mapped IPv6 addresses

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-08 · updated 2026-07-24
Weakness: CWE-180

Description

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.

Affected products

honojs hono: through 4.12.11

References

https://github.com/honojs/hono/commit/48fa2233bc092f650119f42df043050737cabf39
https://github.com/honojs/hono/releases/tag/v4.12.12
https://github.com/honojs/hono/security/advisories/GHSA-xpcf-pg52-r92g

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