# CVE-2020-28493: Regular Expression Denial of Service (ReDoS) in Jinja2

Source: https://junglewise.ai/threats/cve-2020-28493-regular-expression-denial-of-service-redos-in-jinja2  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-02-01  
License: CC BY 4.0 with a link back

CVE-2020-28493 · Severity: low · CVSS 3.1 · Published 2021-02-01

This affects the package jinja2 from 0.0.0 and before 2.11.3. The ReDoS vulnerability is mainly due to the `_punctuation_re regex` operator and its use of multiple wildcards. The last wildcard is the most exploitable as it searches for trailing punctuation. This issue can be mitigated by Markdown to format user content instead of the urlize filter, or by implementing request timeouts and limiting process memory.

Technologies: [jinja2 (PyPI)](https://junglewise.ai/threats/technologies/jinja2). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2020-28493 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2020-28493 being exploited in the wild.

**How severe is CVE-2020-28493?** Low severity, with a CVSS score of 3.1, published 1 February 2021.

**Which products and versions are affected?** jinja2 (PyPI) ECOSYSTEM:introduced=0,fixed=2.11.3.

**Is there a fix for CVE-2020-28493?** Yes. jinja2 (PyPI): upgrade to 2.11.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2020-28493?** Check whether you run jinja2 (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

- jinja2 (PyPI): upgrade to 2.11.3 or later

  ```sh
  pip install "jinja2>=2.11.3"
  ```


## Affected products

- jinja2 (PyPI) ECOSYSTEM:introduced=0,fixed=2.11.3

## Identifiers

- CVE-2020-28493
- GHSA-g3rq-g295-4j3m
- PYSEC-2021-66

## Related threats

- [PYSEC-2026-1471 - Jinja2 vulnerable to sandbox breakout through attr filter selecting format method](https://junglewise.ai/threats/cve-2025-27516-jinja2-vulnerable-to-sandbox-breakout-through-attr-filter)
- [PYSEC-2026-1475 - Jinja has a sandbox breakout through indirect reference to format method](https://junglewise.ai/threats/cve-2024-56326-jinja-has-a-sandbox-breakout-through-indirect-reference-to-format)
- [PYSEC-2026-1472 - Jinja has a sandbox breakout through malicious filenames](https://junglewise.ai/threats/cve-2024-56201-jinja-has-a-sandbox-breakout-through-malicious-filenames)
- [PYSEC-2026-1474 - Jinja vulnerable to HTML attribute injection when passing user input as keys to xmlattr filter](https://junglewise.ai/threats/cve-2024-34064-jinja-vulnerable-to-html-attribute-injection-when-passing-user)
- [PYSEC-2026-1473 - Jinja vulnerable to HTML attribute injection when passing user input as keys to xmlattr filter](https://junglewise.ai/threats/cve-2024-22195-jinja-vulnerable-to-html-attribute-injection-when-passing-user)