Unauthenticated access-control bypass via oversized IPv4 octets
Published Jan 27, 2026 · Updated Jan 27, 2026
IP address validation bypass in Hono before 4.11.7 allows remote attackers to evade IP-based access controls with malformed IPv4 input. The IPV4_REGEX pattern accepts octets above 255, and convertIPv4ToBinary carries overflow bits into adjacent octets, making distinct addresses collide. Exploitation requires IP Restriction Middleware to trust a client-controlled address such as X-Forwarded-For; the result is unauthorized access, not code execution.
Summary
What happened
IP address validation bypass in Hono before 4.11.7 allows remote attackers to evade IP-based access controls with malformed IPv4 input. The IPV4_REGEX pattern accepts octets above 255, and convertIPv4ToBinary carries overflow bits into adjacent octets, making distinct addresses collide. Exploitation requires IP Restriction Middleware to trust a client-controlled address such as X-Forwarded-For; the result is unauthorized access, not code execution.
The record
- CVE
- CVE-2026-24398
- Published
- Jan 27, 2026
- Updated
- Jan 27, 2026
- Vendor
- Hono
- Product
- Hono
- Classifications
- CWE-185, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 27, 2026CVE publishedPublication date reported by the CVE source.
- Jan 27, 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=< 4.11.7
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
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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