CVE-2026-4926

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.

Database specific

{
    "cwe_ids": [
        "CWE-1333",
        "CWE-400"
    ],
    "unresolved_ranges": [
        {
            "source": "AFFECTED_FIELD",
            "extracted_events": [
                {
                    "introduced": "8.0.0"
                },
                {
                    "fixed": "8.4.0"
                }
            ]
        }
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4926.json",
    "cna_assigner": "openjs"
}

References

Affected packages

Git / github.com/pillarjs/path-to-regexp

Affected ranges

Type

GIT

Repo

https://github.com/pillarjs/path-to-regexp

Events

Introduced

ed1095e0fa78a692e7f3d489e383e7bb1f9d2cc4

Fixed

34cb451ddaeea4783a2fe60579ffb3e4ccfc73a7

Database specific

{
    "cpe": "cpe:2.3:a:pillarjs:path-to-regexp:*:*:*:*:*:node.js:*:*",
    "source": "CPE_FIELD",
    "extracted_events": [
        {
            "introduced": "8.0.0"
        },
        {
            "fixed": "8.4.0"
        }
    ]
}

Affected versions

v8.*

v8.0.0

v8.1.0

v8.2.0

v8.3.0

Database specific

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-4926.json"