CVE-2023-30608: Sqlparse Python Module DoS Vulnerability

CVE-2023-30608 Overview

CVE-2023-30608 is a Regular Expression Denial of Service (ReDoS) vulnerability affecting sqlparse, a widely-used non-validating SQL parser module for Python. The vulnerability exists in the SQL parser's string matching regular expressions, which can be exploited to cause excessive CPU consumption and application denial of service when processing specially crafted input.

Critical Impact

Applications using vulnerable versions of sqlparse can be rendered unresponsive through malicious SQL input, potentially causing service outages in web applications, data processing pipelines, and other systems relying on SQL parsing functionality.

Affected Products

• sqlparse versions prior to 0.4.4
• Debian Linux 10.0 (Buster)
• Any Python application using vulnerable sqlparse versions

Discovery Timeline

• 2023-04-18 - CVE-2023-30608 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2023-30608

Vulnerability Analysis

The vulnerability stems from inefficient regular expression patterns used in sqlparse's lexer for parsing string literals within SQL statements. The problematic regex patterns were introduced in commit e75e358 and involve the handling of escaped backslashes within single-quoted and double-quoted strings.

ReDoS attacks exploit the computational complexity of certain regex patterns. When a regex engine encounters ambiguous patterns with overlapping possibilities, it can exhibit exponential time complexity during backtracking. In this case, the regex patterns for handling escaped characters in SQL strings (\\\\ sequences) created conditions where crafted input could cause the regex engine to enter catastrophic backtracking.

The vulnerability was discovered by @erik-krogh from GitHub Security Lab (GHSL), demonstrating the importance of automated security scanning for regex-based vulnerabilities in parsing libraries.

Root Cause

The root cause lies in the regular expression patterns within sqlparse/keywords.py that handle string literal parsing. The original vulnerable patterns contained redundant escape sequence handling:

• Single-quoted strings: '(''|\\\\|\\'|[^'])*'
• Double-quoted strings: "(""|\\\\|\\"|[^"])*"

These patterns included separate handling for escaped backslashes (\\\\) alongside other escape sequences, creating overlapping match possibilities that could trigger exponential backtracking when processing strings with specific character combinations.

Attack Vector

An attacker can exploit this vulnerability remotely by submitting maliciously crafted SQL strings to any application that uses sqlparse for input processing. The attack requires no authentication or special privileges—any input pathway that reaches the sqlparse parser can serve as an attack vector.

The attack works by providing SQL strings containing carefully crafted sequences of backslashes and quote characters that maximize regex backtracking. As the regex engine attempts to match these patterns, CPU usage spikes dramatically, potentially consuming all available processing resources and denying service to legitimate users.

# Vulnerable regex patterns (from sqlparse/keywords.py before fix)
# These patterns contained redundant escape handling that enabled ReDoS
(r"'(''|\\\\|\\'|[^'])*'", tokens.String.Single),
(r'"(""|\\\\|\\"|[^"])*"', tokens.String.Symbol),

# Fixed regex patterns (after commit c457abd5f)
# Removed unnecessary \\\\  pattern to eliminate ReDoS condition
(r"'(''|\\'|[^'])*'", tokens.String.Single),
(r'"(""|\\"|[^"])*"', tokens.String.Symbol),

Source: GitHub Commit Update

Detection Methods for CVE-2023-30608

Indicators of Compromise

• Unusual CPU spikes in application processes that utilize sqlparse for SQL parsing
• Slow or unresponsive web applications or APIs that process SQL queries
• Timeout errors in database-related operations or SQL query logging systems
• Thread or process exhaustion in Python applications handling SQL input

Detection Strategies

• Monitor application CPU utilization for anomalous sustained spikes correlating with SQL input processing
• Implement request timeout monitoring for endpoints that accept SQL-like input
• Use dependency scanning tools (e.g., pip-audit, safety, Snyk) to identify vulnerable sqlparse versions in your environment
• Review application logs for timeout patterns or worker process restarts in SQL parsing components

Monitoring Recommendations

• Configure application performance monitoring (APM) alerts for regex-related CPU consumption patterns
• Implement request-level timeouts on any endpoint that processes user-supplied SQL
• Establish baseline metrics for SQL parsing operations to detect anomalous processing times
• Deploy SentinelOne Singularity Platform for real-time detection of resource exhaustion attacks targeting Python applications

How to Mitigate CVE-2023-30608

Immediate Actions Required

• Upgrade sqlparse to version 0.4.4 or later immediately using pip install --upgrade sqlparse
• Audit all Python applications and dependencies for vulnerable sqlparse versions
• Implement input validation and length limits on SQL input fields as a defense-in-depth measure
• Consider implementing request timeouts for SQL parsing operations until patching is complete

Patch Information

The vulnerability has been fixed in sqlparse version 0.4.4 through commit c457abd5f097dd13fb21543381e7cfafe7d31cfb. The fix removes unnecessary regex components that were causing the ReDoS condition. According to the GitHub Security Advisory GHSA-rrm6-wvj7-cwh2, users are strongly advised to upgrade as there are no known workarounds for this vulnerability.

Debian users should apply the security updates referenced in the Debian LTS Announcement May 2023 and Debian LTS Announcement December 2024.

Workarounds

• No official workarounds are available according to the vendor advisory—upgrading is the only recommended remediation
• As a temporary defensive measure, implement strict input length validation before SQL parsing
• Consider implementing regex timeout mechanisms at the application level if immediate upgrading is not possible
• Rate-limit endpoints that process SQL input to minimize denial of service impact

# Upgrade sqlparse to the patched version
pip install --upgrade sqlparse>=0.4.4

# Verify installed version
pip show sqlparse | grep Version

# For requirements.txt, update to:
# sqlparse>=0.4.4