CVE-2026-24398 is a medium-severity (CVSS 4.8) CWE-185 vulnerability in hono. A fix is available for hono — see the affected versions and patch details below.
Hono's IPv4 address validation bypass in IP Restriction Middleware allows IP spoofing
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-24398.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
hononpmDescription
Summary
IP Restriction Middleware in Hono is vulnerable to an IP address validation bypass. The IPV4_REGEX pattern and convertIPv4ToBinary function in src/utils/ipaddr.ts do not properly validate that IPv4 octet values are within the valid range of 0-255, allowing attackers to craft malformed IP addresses that bypass IP-based access controls.
Details
The vulnerability exists in two components:
- Permissive regex pattern: The
IPV4_REGEX (/^[0-9]{0,3}\.[0-9]{0,3}\.[0-9]{0,3}\.[0-9]{0,3}$/)accepts octet values greater than 255 (e.g.,999). - Unsafe binary conversion: The
convertIPv4ToBinaryfunction does not validate octet ranges before performing bitwise operations. When an octet exceeds 255, it overflows into adjacent octets during the bit-shift calculation.
For example, the IP address 1.2.2.355 is accepted and converts to the same binary value as 1.2.3.99:
355=256 + 99=0x163- After bit-shifting:
(1 << 24) + (2 << 16) + (2 << 8) + 355=0x01020363=1.2.3.99
Impact
An attacker can bypass IP-based restrictions by crafting malformed IP addresses:
- Blocklist bypass: If
1.2.3.0/24is blocked, an attacker can use1.2.2.355(or similar) to bypass the restriction. - Allowlist bypass: Requests from unauthorized IP ranges may be incorrectly permitted.
This is exploitable when the application relies on client-provided IP addresses (e.g., X-Forwarded-For header) for access control decisions.
Affected Components
- IP Restriction Middleware
src/utils/ipaddr.ts:IPV4_REGEX,convertIPv4ToBinary,distinctRemoteAddr
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | hono | all versions | 4.11.7npm install hono@4.11.7 |
Affected Products
honohonoDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update hono to 4.11.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-24398 is resolved across your whole dependency graph.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
Frequently Asked Questions
Is CVE-2026-24398 in your dependencies?
Find it across npm, including transitive dependencies.