CVE Catalog

CVE-2026-4926

HighCVSS 7.5
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Elevated risk
0.79%

54th percentile - higher than 54% of all known CVEs

Summary

A vulnerability in a routing library causes a bad regular expression when multiple sequential optional groups (curly brace syntax) are used, e.g., `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, leading to denial of service (DoS).

Risk Assessment

An attacker can exploit this by sending requests with crafted route patterns, causing excessive resource consumption and making the application unavailable.

Recommendation

Update the library to version 8.4.0 or later immediately. As a workaround, limit the number of sequential optional groups in route patterns and avoid passing user-controlled input as route patterns.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS