Vulnerability in Markdown-It Linkify-It
CVE-2026-48801
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 class: ReDoS (Regular Expression Denial of Service)
EPSS: 0.004 (29.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Markdown-it Linkify-it — versions < 5.0.1
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-48801?
- CVE-2026-48801 is a high-severity vulnerability in Markdown-It Linkify-It, classified under Inefficient Regular Expression Complexity. CVSS score: 7.5/10. Published 2026-07-14.
- How severe is CVE-2026-48801?
- High severity. CVSS v3 base score is 7.5 out of 10.