CVE-2026-42338
CVE-2026-42338 is a Cross-site Scripting (XSS) vulnerability in ip-address. O3 Security confirms whether CVE-2026-42338 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
ip-address: XSS in Address6 HTML-emitting methods
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42338.
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.
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.
ip-addressnpmDescription
ip-address is a library for parsing and manipulating IPv4 and IPv6 addresses in JavaScript. Prior to 10.1.1, Address6.group() and Address6.link() do not HTML-escape attacker-controlled content before embedding it in the HTML strings they return, and AddressError.parseMessage (emitted by the Address6 constructor for invalid input) can contain unescaped attacker-controlled content in one branch. An application that (1) passes untrusted input to Address6 and (2) renders the output of these methods, or the thrown error's parseMessage, as HTML (e.g. via innerHTML) is vulnerable to cross-site scripting. This vulnerability is fixed in 10.1.1.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | ip-address | all versions | 10.1.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ip-address. 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 ip-address to 10.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42338 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 CVE-2026-42338 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 CVE-2026-42338. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability in the `ip-address` JavaScript library is rated as Important. It allows for cross-site scripting (XSS) when an application processes untrusted input through the `Address6` constructor and subsequently renders the unescaped output of methods like `Address6.group()`, `Address6.link()`, or…
Frequently Asked Questions
Is CVE-2026-42338 in your dependencies?
O3 detects CVE-2026-42338 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.