CVE-2021-32839: Sqlparse Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-p5w8-wqhj-9hhf
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CVSS 7.5
CWE-400
Published
Advisory Summary

CVE-2021-32839 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Sqlparse libraries in the PyPI ecosystem. The issue involves stripcomments filter contains a regular expression that is vulnerable to redos (regular expression denial of service). Remediation is available by upgrading affected packages to version 0.4.2.

CVE-2021-32839 at a Glance

CVE Identifier CVE-2021-32839
GHSA Identifier GHSA-p5w8-wqhj-9hhf
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Sqlparse
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2021-32839

To remediate this vulnerability, upgrade all affected Sqlparse dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

sqlparse fixed: 0.4.2 
pip install sqlparse>=0.4.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show sqlparse

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-32839, inspect your installed packages using pip:

pip show sqlparse

Analyze the terminal output to locate any version of Sqlparse in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.4.2), your application is affected.

Note: The pip show sqlparse command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Sqlparse, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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)

CVE-2021-32839 Affected Sqlparse Versions

1 component(s)
Fixed Versions:
0.4.2
Product / Package Ecosystem Affected Versions Fixed Version
sqlparse
pypi/sqlparse
PyPI
≥ 0.4.0
< 0.4.2
0.4.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/andialbrecht/sqlparse/security/advisories/GHSA-p5w8-wqhj-9hhf
NVD — CVE-2021-32839 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-32839
Security Fix Commit FIX COMMIT
https://github.com/andialbrecht/sqlparse/commit/8238a9e450ed1524e40cb3a8b0b3c00606903aeb
Sqlparse Source Repository REPOSITORY
https://github.com/andialbrecht/sqlparse
Sqlparse Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/sqlparse/PYSEC-2021-333.yaml
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2024/12/msg00022.html
GitHub Advisory / Wiki ADVISORY
https://securitylab.github.com/advisories/GHSL-2021-107-andialbrecht-sqlparse

Frequently Asked Questions

What is CVE-2021-32839?
CVE-2021-32839 is a security vulnerability in Sqlparse involving StripComments filter contains a regular expression that is vulnerable to ReDOS (Regular Expression Denial of Service) under CWE-400: Uncontrolled Resource Consumption.
Which Sqlparse versions are affected?
Affected versions include releases prior to 0.4.2 across affected packages: sqlparse.
What version fixes CVE-2021-32839?
Upgrading to 0.4.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is sqlparse affected?
Yes, sqlparse is affected in releases prior to 0.4.2. Upgrade your dependency to 0.4.2 or later.
What is the CVSS score of CVE-2021-32839?
CVE-2021-32839 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2021-32839?
CVE-2021-32839 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check PyPI dependencies for CVE-2021-32839?
Run the dependency tree command: 'pip show sqlparse'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-p5w8-wqhj-9hhf",
  "modified" : "2025-11-04T16:35:21Z",
  "published" : "2021-09-10T17:56:06Z",
  "aliases" : [ "CVE-2021-32839" ],
  "summary" : "StripComments filter contains a regular expression that is vulnerable to ReDOS (Regular Expression Denial of Service)",
  "details" : "### Impact\nThe 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.\n\n### Patches\nThe issues has been fixed in sqlparse 0.4.2.\n\n### Workarounds\nOnly 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.\n\n### References\nThis 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/). \n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [sqlparse issue tracker](https://github.com/andialbrecht/sqlparse/issues)\n* Email us at [albrecht.andi@gmail.com](mailto:albrecht.andi@gmail.com)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "sqlparse"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.4.0"
      }, {
        "fixed" : "0.4.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/andialbrecht/sqlparse/security/advisories/GHSA-p5w8-wqhj-9hhf"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-32839"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/andialbrecht/sqlparse/commit/8238a9e450ed1524e40cb3a8b0b3c00606903aeb"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/andialbrecht/sqlparse"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/sqlparse/PYSEC-2021-333.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2024/12/msg00022.html"
  }, {
    "type" : "ADVISORY",
    "url" : "https://securitylab.github.com/advisories/GHSL-2021-107-andialbrecht-sqlparse"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-09-10T17:13:29Z",
    "nvd_published_at" : "2021-09-20T17:15:00Z"
  }
}