# CVE-2026-111758: markdown-it quadratic-time rendering of unclosed link reference

Source: https://junglewise.ai/threats/cve-2026-111758-markdown-it-quadratic-time-rendering-of-a-single-multi-line-link  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-20. Updated: 2026-10-20  
License: CC BY 4.0 with a link back

CVE-2026-111758 · Severity: high · CVSS 7.5 · Published 2026-10-20

markdown-it is a Markdown parser widely used in web applications, documentation systems, and chat interfaces. An attacker can send specially crafted Markdown with an unclosed link reference definition to cause the parser to consume excessive CPU time, blocking the application's event loop for seconds and causing denial of service. A 400 KB malicious input stalls processing for about 18 seconds.

Technologies: [Markdown-It](https://junglewise.ai/threats/technologies/markdown-it-markdown-it), [markdown-it (npm)](https://junglewise.ai/threats/technologies/markdown-it). Vendors: [Markdown-It](https://junglewise.ai/threats/vendors/markdown-it), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-111758 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-111758 being exploited in the wild.

**How severe is CVE-2026-111758?** High severity, with a CVSS score of 7.5, published 20 October 2026.

**Which products and versions are affected?** Markdown-It 14.0.0 through 15.0.2; markdown-it (npm) >= 14.1.0, < 14.3.3, SEMVER:introduced=14.1.0,fixed=14.3.3.

**Is there a fix for CVE-2026-111758?** Yes. markdown-it (npm): upgrade to 14.3.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-111758 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-111758?** Check whether you run Markdown-It or markdown-it (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- markdown-it (npm): upgrade to 14.3.3 or later

  ```sh
  npm install markdown-it@14.3.3
  ```


## Technical details

The reference.ts rule accumulates continuation lines using string concatenation (str += lineContent), then repeatedly calls charCodeAt and slice on the result, forcing V8 to flatten cons-strings and copy all accumulated content, creating O(n²) behavior. The vulnerability is reachable via default options without any special configuration. A fix requires tracking positions in the source buffer or collecting line slices in an array instead of concatenating strings.

## Affected products

- markdown-it markdown-it 14.0.0 through 15.0.2

## Identifiers

- CVE-2026-111758
- GHSA-gfr2-rv44-r23c

## Timeline

- 2026-10-20: disclosed: GHSA-gfr2-rv44-r23c published

## Related threats

- [markdown-it: Quadratic-time denial of service in inline HTML parsing with html enabled](https://junglewise.ai/threats/cve-2026-111766-markdown-it-is-a-markdown-parser-prior-to-14-3-3-and-15-0-3-when)
- [markdown-it quadratic ReDoS in smartquotes](https://junglewise.ai/threats/cve-2026-111759-markdown-it-is-a-markdown-parser-prior-to-14-3-2-and-15-0-2-when)
- [markdown-it quadratic performance degradation in linkify processing](https://junglewise.ai/threats/markdown-it-linkify-true-has-two-quadratic-paths-so-a-few-hundred-kb-of-a1cf8480)
- [markdown-it denial of service in smartquotes rule](https://junglewise.ai/threats/cve-2026-48988-markdown-it-denial-of-service-in-smartquotes-rule)
- [markdown-it ReDoS in linkify regex](https://junglewise.ai/threats/cve-2026-2327-markdown-it-redos-in-linkify-function)