CVE-2026-39409

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

CVSS 4.0 6.3 MEDIUMEUVD CVSS 4.0 6.3 CVSS 4.0 · [email protected] · Secondary 6.3 MEDIUMCVSS 3.1 · [email protected] · Primary 5.3 MEDIUMCVSS_V3 CVSS_V4 Publisher rating MODERATEFixed by hono 4.12.12KEV status unknown

Original advisory

cve-program · CVE-2026-39409

Published

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.

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euvd · EUVD-2026-20497

Published

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nvd · CVE-2026-39409

Published

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osv · GHSA-xpcf-pg52-r92g

Published

## Summary `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. ## Details The middleware classifies client addresses based on their textual form. Addresses containing "`:`" are treated as IPv6, including IPv4-mapped IPv6 addresses such as `::ffff:127.0.0.1`. These addresses are not normalized to IPv4 before matching. As a result: * IPv4 static rules (e.g. `127.0.0.1`) do not match because the raw string differs * IPv4 CIDR rules (e.g. `127.0.0.0/8`, `10.0.0.0/8`) are skipped because the address is treated as IPv6 For example, with: `denyList: ['127.0.0.1']` a request from `127.0.0.1` may be represented as `::ffff:127.0.0.1` and bypass the deny rule. This behavior commonly occurs in Node.js environments where IPv4 clients are exposed as IPv4-mapped IPv6 addresses. ## Impact Applications that rely on IPv4-based `ipRestriction()` rules may incorrectly allow or deny requests. In affected deployments, a denied IPv4 client may bypass access restrictions. Conversely, legitimate clients may be rejected when using IPv4 allow lists.

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Affected versions, risk and source history

Exploitation and risk

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15 Nov 2026 11:06:14 UTC