CVE-2026-3455
CVE-2026-3455 is a Cross-site Scripting (XSS) vulnerability in mailparser. O3 Security confirms whether CVE-2026-3455 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
mailparser vulnerable to Cross-site Scripting
Blast Radius
mailparserReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Versions of the package mailparser before 3.9.3 are vulnerable to Cross-site Scripting (XSS) via the textToHtml() function due to the improper sanitisation of URLs in the email content. An attacker can execute arbitrary scripts in victim browsers by adding extra quote " to the URL with embedded malicious JavaScript code.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | mailparser | all versions | 3.9.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mailparser. 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 mailparser to 3.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-3455 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-2026-3455 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-2026-3455. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-3455 in your dependencies?
O3 detects CVE-2026-3455 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.