Description
Impact: A bad regular expression is generated any time you have three or more parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b-:c or /:a-:b-:c-:d. The backtrack protection added in [email protected] only prevents ambiguity for two parameters. With three or more, the generated lookahead does not block single separator characters, so capture groups overlap and cause catastrophic backtracking. Patches: Upgrade to [email protected] Custom regex patterns in route definitions (e.g., /:a-:b([^-/]+)-:c([^-/]+)) are not affected because they override the default capture group. Workarounds: All versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b-:c to /:a-:b([^-/]+)-:c([^-/]+). If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length.
INFO
Published Date :
2026-03-26T16:16:25.501Z
Last Modified :
2026-03-26T16:52:14.893Z
Source :
openjs
AFFECTED PRODUCTS
The following products are affected by CVE-2026-4867 vulnerability.
| Vendors | Products |
|---|---|
| Path-to-regexp |
|
| Pillarjs |
|
REFERENCES
Here, you will find a curated list of external links that provide in-depth information to CVE-2026-4867.
