path-to-regexp vulnerable to Denial of Service via sequential optional groups
### 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.
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describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-4926US | — | — | ||
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 exponent… | ||||
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references
External citations — patches, advisories, analysis.
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