# CVE-2026-4867: node-path-to-regexp: Impact:  A bad regular expression is generated any time you have three or more parameters within a single segment, se...

CVE-2026-4867 is fixed in node-path-to-regexp on 1 platform, first by DEBIAN-CVE-2026-4867, released March 26, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-4867
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0052
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 26, 2026

## 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 path-to-regexp@0.1.12 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 path-to-regexp@0.1.13  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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | node-path-to-regexp Debian 12.15 (bookworm) | 1.0.1-1 | [DEBIAN-CVE-2026-4867](https://patchblox.com/security/data/fix/linux/debian-cve-2026-4867.md) | Mar 26, 2026 |
| Linux | node-path-to-regexp Debian 13.5 (trixie) | 1.0.1-1 | [DEBIAN-CVE-2026-4867](https://patchblox.com/security/data/fix/linux/debian-cve-2026-4867.md) | Mar 26, 2026 |
| Linux | node-path-to-regexp Debian 14 | 1.0.1-1 | [DEBIAN-CVE-2026-4867](https://patchblox.com/security/data/fix/linux/debian-cve-2026-4867.md) | Mar 26, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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