CVE-2021-32839Public exploitNetwork attack vector

Processing hang via exponential comment-regex backtracking

Published Sep 20, 2021 · Updated Nov 3, 2025

Regular expression denial of service in sqlparse 0.4.0 through 0.4.1 allows attackers to cause a processing hang via crafted SQL comments. The StripComments filter's line-break regex treats CRLF as an alternative to its individual characters, causing exponential backtracking on repeated CRLF sequences. The affected path runs only when comment stripping is enabled, and attacker-controlled SQL comments can monopolize CPU and hang the consuming process.

CVSS severity7.5
High
EPSS probability2.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Regular expression denial of service in sqlparse 0.4.0 through 0.4.1 allows attackers to cause a processing hang via crafted SQL comments. The StripComments filter's line-break regex treats CRLF as an alternative to its individual characters, causing exponential backtracking on repeated CRLF sequences. The affected path runs only when comment stripping is enabled, and attacker-controlled SQL comments can monopolize CPU and hang the consuming process.

The record

CVE
CVE-2021-32839
Published
Sep 20, 2021
Updated
Nov 3, 2025
Vendor
Andi Albrecht
Product
sqlparse
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 0.4.0, < 0.4.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Andi Albrecht · sqlparseversion=>= 0.4.0, < 0.4.2

Published CVSS scores

7.5GitLab Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo