CVE-2026-4867
Description
A flaw was found in path-to-regexp. A remote attacker could exploit this vulnerability by crafting a malicious URL with three or more parameters in a single segment, separated by non-period characters. This causes the component to generate a bad regular expression, leading to catastrophic backtracking. The overlapping capture groups can consume excessive processing resources, resulting in a Denial of Service (DoS) for the affected application.
Mitigation
To mitigate this issue, applications using `path-to-regexp` can implement custom regular expressions for parameters beyond the first in a single URL segment. For example, a route like `/:a-:b-:c` can be rewritten as `/:a-:b([^-/]+)-:c([^-/]+)`. Alternatively, limiting the maximum length of incoming URLs can also reduce the risk of exploitation. These changes require application-level configuration and may necessitate a service restart to take effect.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | Low | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU)
Attackers can create crafted inputs that intentionally cause the regular expression to use excessive backtracking in a way that causes the CPU consumption to spike.
Frequently Asked Questions
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