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 [email protected]