# CVE-2021-26813: markdown2 Regular Expression Denial of Service

Source: https://junglewise.ai/threats/cve-2021-26813-markdown2-regular-expression-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-03-03  
License: CC BY 4.0 with a link back

CVE-2021-26813 · Severity: low · CVSS 3.1 · Published 2021-03-03

markdown2 >=1.0.1.18, fixed in 2.4.0, is affected by a regular expression denial of service vulnerability. If an attacker provides a malicious string, it can make markdown2 processing difficult or delayed for an extended period of time.

Technologies: [markdown2 (PyPI)](https://junglewise.ai/threats/technologies/markdown2). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2021-26813 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-26813 being exploited in the wild.

**How severe is CVE-2021-26813?** Low severity, with a CVSS score of 3.1, published 3 March 2021.

**Which products and versions are affected?** markdown2 (PyPI) ECOSYSTEM:introduced=1.0.1.18,fixed=2.4.0.

**Is there a fix for CVE-2021-26813?** Yes. markdown2 (PyPI): upgrade to 2.4.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-26813?** Check whether you run markdown2 (PyPI) 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

- markdown2 (PyPI): upgrade to 2.4.0 or later

  ```sh
  pip install "markdown2>=2.4.0"
  ```


## Affected products

- markdown2 (PyPI) ECOSYSTEM:introduced=1.0.1.18,fixed=2.4.0

## Identifiers

- CVE-2021-26813
- GHSA-jr9p-r423-9m2r
- PYSEC-2021-20

## Related threats

- [XSS in python-markdown2](https://junglewise.ai/threats/cve-2020-11888-xss-in-python-markdown2)
- [PYSEC-2020-235 - python-markdown2 before 1.0.1.14 has multiple cross-site scripting (XSS) issues.](https://junglewise.ai/threats/cve-2009-3724-cross-site-scripting-in-markdown2-for-python)
- [markdown2 is vulnerable to cross-site scripting](https://junglewise.ai/threats/cve-2018-5773-markdown2-is-vulnerable-to-cross-site-scripting)