linkify-it <=5.0.1 O(N2) DoS via link matching (markdown-it)
CVE-2026-48801 Published on July 14, 2026
linkify-it: Quadratic algorithmic complexity in LinkifyIt#match scan loop
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.
Vulnerability Analysis
CVE-2026-48801 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. An automatable proof of concept (POC) exploit exists. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
What is a ReDoS Vulnerability?
The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles. Some regular expression engines have a feature called "backtracking". If the token cannot match, the engine "backtracks" to a position that may result in a different token that can match. Backtracking becomes a weakness if all of these conditions are met:
CVE-2026-48801 has been classified to as a ReDoS vulnerability or weakness.
Affected Versions
markdown-it linkify-it Version < 5.0.1 is affected by CVE-2026-48801Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.