Vulnerability · Published Apr 8, 2026 · Assigned by GitHub_M

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

Medium 6.3

In plain English

A medium-severity security flaw in hono from honojs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 29% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.3Medium

Exploit odds (30 days)0.3%top 71.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	hono	4.12.12	GHSA-xpcf-pg52-r92g

Affected products (as reported)

Vendor	Product	Versions
honojs	hono	< 4.12.12

Weakness: CWE-180 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

References

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