IP restriction bypass via non-canonical IPv6 comparison
Published May 28, 2026 · Updated May 28, 2026
Access-control bypass in Hono before 4.12.21 allows remote attackers to evade static IP deny rules with non-canonical IPv6 addresses. The middleware canonicalizes each configured static rule but compares the request-time address as an unnormalized string, then skips CIDR matching for rules without prefixes. Exploitation requires ipRestriction() with a static rule and an IP source, often a proxy or custom getIP function, that supplies an equivalent address in a different IPv6 form.
Summary
What happened
Access-control bypass in Hono before 4.12.21 allows remote attackers to evade static IP deny rules with non-canonical IPv6 addresses. The middleware canonicalizes each configured static rule but compares the request-time address as an unnormalized string, then skips CIDR matching for rules without prefixes. Exploitation requires ipRestriction() with a static rule and an IP source, often a proxy or custom getIP function, that supplies an equivalent address in a different IPv6 form.
The record
- CVE
- CVE-2026-47674
- Published
- May 28, 2026
- Updated
- May 28, 2026
- Vendor
- Hono
- Product
- Hono
- Classifications
- CWE-185, CWE-1289, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 28, 2026CVE publishedPublication date reported by the CVE source.
- May 28, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 4.12.21
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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