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Vulnerability record · CVE-2026-48801 · published 14 July 2026

CVE-2026-48801: Markdown-it linkify-it inefficient regular expression (redos) vulnerability

MMarkdown It · Linkify It

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.

8.7 CVSS 4.0 High EPSS 0.52% · top 58.5% CWE-1333 · Inefficient regular expression (ReDoS)
8.7CVSS 4.0 base score
0.52%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References, 2 tagged exploit
6 Aug 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/markdown-it/linkify-it/commit/6be6d15e0641bf1daeaa977d500cabc743166159 Patch
https://github.com/markdown-it/linkify-it/security/advisories/GHSA-22p9-wv53-3rq4 ExploitVendor Advisory
https://github.com/markdown-it/linkify-it/security/advisories/GHSA-22p9-wv53-3rq4 ExploitVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.5CVE-2026-59887Markdown-it linkify-it vulnerabilitylinkify-it is a links recognition library with full Unicode support. Prior to 5.0.2, the mailto: schema validator used by .test() and .match() can be…EPSS 0.64%

Source: NIST National Vulnerability Database (record CVE-2026-48801), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.