GHSA-xrhx-7g5j-rcj5 is a medium-severity (CVSS 5.3) CWE-185 vulnerability in hono. O3 Security confirms whether GHSA-xrhx-7g5j-rcj5 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Hono: IP Restriction bypasses static deny rules for non-canonical IPv6
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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 GHSA-xrhx-7g5j-rcj5.
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.
How urgent is this, really
GHSA-xrhx-7g5j-rcj5 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 371,972 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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
The ip-restriction middleware (hono/ip-restriction) compares incoming IP addresses against configured deny and allow rules using string equality after partial normalization. Non-canonical IPv6 representations of an address already listed in a static rule — such as compressed forms, explicit-zero forms, or hex-notation IPv4-mapped addresses — do not match the normalized rule entry, causing the rule to be silently skipped.
Details
When the rule matcher is built, each configured IP rule is normalized to a canonical string form. Incoming IP addresses received at request time are then compared against those canonical strings without applying the same normalization. Because IPv6 permits multiple syntactically different representations of the same numeric address, a non-canonical form of a denied address fails the string lookup and proceeds to the CIDR check, which also finds no match for rules registered as static (no prefix length). The request is then allowed.
Affected non-canonical forms include:
- Compressed versus expanded notation (
2001:db8::1vs2001:db8:0:0:0:0:0:1) - Hex-notation IPv4-mapped addresses (
::ffff:7f00:1vs::ffff:127.0.0.1) - Zone identifier suffixes (e.g.,
fe80::1%eth0)
Additionally, invalid IP address strings provided as the remote address are not rejected and may result in unexpected allow or deny behavior.
This issue arises when applications use ipRestriction() with static (non-CIDR) rules and the IP address source can supply addresses in non-canonical IPv6 form.
Impact
A request from an IP address covered by a static deny rule may bypass the restriction if the address is presented in a non-canonical IPv6 form.
This may lead to:
- Unauthorized access to endpoints intended to be restricted to specific IP addresses
- Bypass of IP-based access controls in environments where the runtime or an upstream proxy provides source addresses in a form that differs from the canonical form used in the rule configuration
This issue affects applications using hono/ip-restriction with static deny rules for IPv4 or IPv6 addresses, particularly when the source address is derived from proxy headers or custom getIP implementations that may return non-canonical forms.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | hono | all versions | 4.12.21 |
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 4.12.21 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-xrhx-7g5j-rcj5 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-xrhx-7g5j-rcj5 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-xrhx-7g5j-rcj5. 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-xrhx-7g5j-rcj5 in your dependencies?
O3 detects GHSA-xrhx-7g5j-rcj5 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.