StripComments filter contains a regular expression that is vulnerable to ReDOS (Regular Expression Denial of Service)
Impact
The formatter function that strips comments from a SQL contains a regular expression that is vulnerable to 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 query which identifies inefficient regular expressions. You can see the results of the query on python-sqlparse by following this link.
For more information
If you have any questions or comments about this advisory:
- Open an issue in sqlparse issue tracker
- Email us at albrecht.andi@gmail.com
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | sqlparse | >= 0.4.0, < 0.4.2 | 0.4.2 |
References
- https://github.com/andialbrecht/sqlparse/commit/8238a9e450ed1524e40cb3a8b0b3c00606903aeb
- https://github.com/andialbrecht/sqlparse/security/advisories/GHSA-p5w8-wqhj-9hhf
- https://nvd.nist.gov/vuln/detail/CVE-2021-32839
- https://github.com/andialbrecht/sqlparse
- https://github.com/pypa/advisory-database/tree/main/vulns/sqlparse/PYSEC-2021-333.yaml
- https://lists.debian.org/debian-lts-announce/2024/12/msg00022.html
- https://securitylab.github.com/advisories/GHSL-2021-107-andialbrecht-sqlparse
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-400- Platform
- Python (PyPI)
- Package
sqlparse- Disclosed
- 10.09.2021
- Updated
- 11.10.2026 13:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2021-333 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-p5w8-wqhj-9hhf - CC BY 4.0
Vulnerability history: sqlparse
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 9
- First → latest
- 09.2021 09.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 5
- Medium 4
Disclosures per year
- 2021: 1
- 2022: 0
- 2023: 1
- 2024: 1
- 2025: 0
- 2026: 6
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StripComments filter contains a regular expression that is vulnerable to ReDOS (Regular Expression Denial of Service) this entry
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