GHSA-r354-f388-2fhh
MEDIUMHono IPv4 address validation bypass in IP Restriction Middleware allows IP spoofing
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
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 | 4.11.7 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update hono to 4.11.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-r354-f388-2fhh is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-r354-f388-2fhh is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-r354-f388-2fhh. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-r354-f388-2fhh in your dependencies?
O3 detects GHSA-r354-f388-2fhh across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.