CVE-2026-4926
HIGHCVE-2026-4926 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in path-to-regexp. O3 Security confirms whether CVE-2026-4926 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
path-to-regexp vulnerable to Denial of Service via sequential optional groups
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
path-to-regexpnpmDescription
Impact:
A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as {a}{b}{c}:z. The generated regex grows exponentially with the number of groups, causing denial of service.
Patches:
Fixed in version 8.4.0.
Workarounds:
Limit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | path-to-regexp | ≥ 8.0.0&&< 8.4.0 | 8.4.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for path-to-regexp. 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 path-to-regexp to 8.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-4926 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-2026-4926 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-2026-4926. 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-2026-4926 in your dependencies?
O3 detects CVE-2026-4926 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.