Summary
StripComments filter contains a regular expression that is vulnerable to ReDOS (Regular Expression Denial of Service)
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]
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.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2021-32839 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.4.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The issues has been fixed in sqlparse 0.4.2.
Frequently Asked Questions
- What is CVE-2021-32839? CVE-2021-32839 is a high-severity uncontrolled resource consumption vulnerability in sqlparse (pip), affecting versions >= 0.4.0, < 0.4.2. It is fixed in 0.4.2. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2021-32839? CVE-2021-32839 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of sqlparse are affected by CVE-2021-32839? sqlparse (pip) versions >= 0.4.0, < 0.4.2 is affected.
- Is there a fix for CVE-2021-32839? Yes. CVE-2021-32839 is fixed in 0.4.2. Upgrade to this version or later.
- Is CVE-2021-32839 exploitable, and should I be worried? Whether CVE-2021-32839 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-32839 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-32839? Upgrade
sqlparseto 0.4.2 or later.