---
id: CVE-2021-32839
aliases:
  - GHSA-p5w8-wqhj-9hhf
  - PYSEC-2021-333
title: >-
  StripComments filter contains a regular expression that is vulnerable to ReDOS
  (Regular Expression Denial of Service)
summary: >-
  StripComments filter contains a regular expression that is vulnerable to ReDOS
  (Regular Expression Denial of Service)
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
vendor: sqlparse
product: sqlparse
ecosystem: pip
affected:
  - 'sqlparse >= 0.4.0, < 0.4.2'
patched:
  - sqlparse 0.4.2
published: '2021-09-10'
updated: '2026-07-08'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-p5w8-wqhj-9hhf'
references:
  - url: >-
      https://github.com/andialbrecht/sqlparse/security/advisories/GHSA-p5w8-wqhj-9hhf
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-32839'
  - url: >-
      https://github.com/andialbrecht/sqlparse/commit/8238a9e450ed1524e40cb3a8b0b3c00606903aeb
  - url: 'https://github.com/andialbrecht/sqlparse'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/sqlparse/PYSEC-2021-333.yaml
  - url: 'https://lists.debian.org/debian-lts-announce/2024/12/msg00022.html'
  - url: >-
      https://securitylab.github.com/advisories/GHSL-2021-107-andialbrecht-sqlparse
tags:
  - osv
  - pip
epss: 0.02339
epssPercentile: 0.82892
ingestedAt: '2026-07-08T18:25:51.649Z'
---

## Overview

### Impact
The formatter function that strips comments from a SQL contains a regular expression that is vulnerable to [ReDoS](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS) (Regular Expression Denial of Service). The regular expression may cause exponential backtracking on strings containing many repetitions of '\r\n' in SQL comments.

### Patches
The issues has been fixed in sqlparse 0.4.2.

### Workarounds
Only the formatting feature that removes comments from SQL statements is affected by this regular expression. As a workaround don't use the `sqlformat.format` function with keyword `strip_comments=True` or the `--strip-comments` command line flag when using the `sqlformat` command line tool.

### References
This issue was discovered by GitHub team members @erik-krogh and @yoff. It was found using a [CodeQL](https://codeql.github.com/) query which identifies inefficient regular expressions. You can see the results of the query on python-sqlparse by following [this link](https://lgtm.com/query/2223658096471222354/). 

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [sqlparse issue tracker](https://github.com/andialbrecht/sqlparse/issues)
* Email us at [albrecht.andi@gmail.com](mailto:albrecht.andi@gmail.com)

## Affected packages

- `sqlparse >= 0.4.0, < 0.4.2`

## Remediation

Upgrade to a patched release:

- `sqlparse 0.4.2`