High [CVE-2026-48801] Denial of Service via algorithmic complexity vulnerability

linkify-it is a links recognition library with full Unicode support. Prior to 5.0.1, LinkifyIt.prototype.match, the package's primary public API, has O(N²) algorithmic complexity for inputs containing many fuzzy links or emails because the JavaScript-level scan loop re-slices input and re-runs unanchored regex searches on progressively shorter tails.

Any service that synchronously renders untrusted Markdown with linkify:true on a request hot path can inherit a worker-process denial of service triggerable by a tens-of-KB request body. This issue is fixed in version 5.0.1.

This can be exploited by a remote attacker sending a specially crafted request body, leading to a worker-process denial of service (DoS) due to excessive CPU usage when synchronously rendering untrusted Markdown with linkify enabled. This Moderate impact flaw in linkify-it, a link recognition library, can lead to a denial of service in Red Hat products.

The vulnerability arises from an O(N²) algorithmic complexity when processing untrusted Markdown with numerous fuzzy links or emails, potentially causing excessive CPU consumption and worker-process unavailability. This risk is present in services that synchronously render untrusted Markdown with the linkify feature enabled.

Red Hat severity: Moderate — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-1333.