# Marked ReDoS in email address validation

Source: https://junglewise.ai/threats/marked-redos-in-email-address-validation-f7e45a68  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2019-06-05. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

Severity: low · CVSS 3.1 · Published 2019-06-05

Marked is a popular JavaScript Markdown parser used to convert Markdown text into HTML. The library contained a regular expression that could evaluate email addresses in quadratic time, allowing attackers to cause denial of service by crafting specially malformed input that forces excessive processing and crashes the application or node.js process.

Technologies: [marked (npm)](https://junglewise.ai/threats/technologies/npm-marked). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Low severity, with a CVSS score of 3.1, published 5 June 2019.

**Which products and versions are affected?** marked (npm) SEMVER:introduced=0.3.14,fixed=0.6.2.

**Is there a fix for This vulnerability?** Yes. marked (npm): upgrade to 0.6.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network.

**Am I affected?** Check whether you run marked (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

- marked (npm): upgrade to 0.6.2 or later

  ```sh
  npm install marked@0.6.2
  ```


## Technical details

The vulnerability is a Regular Expression Denial of Service (ReDoS) flaw in Marked's inline text parsing regex, specifically in email address validation. The regex performed quadratic-time backtracking when processing malformed email-like patterns, causing catastrophic performance degradation. An unauthenticated attacker on the network can send a specially crafted Markdown document containing problematic email address patterns to trigger excessive CPU consumption and crash the node.js process. The vulnerability was fixed in version 0.6.2 by refactoring the regexes to avoid catastrophic backtracking and quadratic scanning behavior.

## Affected products

- Marked marked 0.3.14 to 0.6.1

## Timeline

- 2019-06-05: disclosed

## References

- [https://github.com/markedjs/marked/pull/1460](https://github.com/markedjs/marked/pull/1460)
- [https://github.com/markedjs/marked/commit/b15e42b67cec9ded8505e9d68bb8741ad7a9590d](https://github.com/markedjs/marked/commit/b15e42b67cec9ded8505e9d68bb8741ad7a9590d)

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