CVE-2026-54284: sqlparse CPU DoS Vulnerability

Executive Intelligence Brief

A vulnerability in the sqlparse library, CVE-2026-54284, with a CVSS score of 8.7, can cause a CPU Denial of Service (DoS) attack when parsing malicious SQL queries. The vulnerability affects all versions of sqlparse, including the latest version 0.5.5. Attackers can exploit this vulnerability by sending crafted SQL queries that can consume excessive CPU resources, leading to a denial of service. The vulnerability has a high severity score and can be exploited remotely without authentication.

Threat Overview

The sqlparse library is a popular Python library used for parsing and formatting SQL queries. The vulnerability is caused by the `TokenList.__init__` method, which materializes the entire subtree on every call, leading to a quadratic time complexity of O(n*depth) per token-group construction. This can cause the parser to spend multiple seconds of CPU before the depth cap raises a `SQLParseError`. The vulnerability can be exploited by sending crafted SQL queries with nested parentheses or CASE WHEN chains.

Technical Deep Dive

Vulnerability Classification

The vulnerability is classified as a Denial of Service (DoS) vulnerability, specifically a CPU DoS attack. The vulnerability is caused by the `TokenList.__init__` method, which has a quadratic time complexity of O(n*depth) per token-group construction.

Root Cause Analysis

The root cause of the vulnerability is the `TokenList.__init__` method calling `super().__init__(None, str(self))`. The `TokenList.__str__` method flattens the entire subtree on every call, and grouping constructs a new `TokenList` for every parenthesis / CASE / list group, so a tree of depth `d` with `n` total tokens performs `O(n*d)` flatten work just to materialize the cached `value` field.

Attack Vector & Chain

The attack vector is a crafted SQL query with nested parentheses or CASE WHEN chains. The query can be sent to a vulnerable application that uses the sqlparse library to parse and format SQL queries. The attack chain involves the following steps: 1. The attacker sends a crafted SQL query to a vulnerable application. 2. The application uses the sqlparse library to parse and format the SQL query. 3. The `TokenList.__init__` method is called, which materializes the entire subtree on every call. 4. The parser spends multiple seconds of CPU before the depth cap raises a `SQLParseError`.

Exploitation Scenario Walkthrough

Scenario: CPU DoS Attack via Malicious SQL Query 1. Reconnaissance: The attacker discovers a vulnerable application that uses the sqlparse library to parse and format SQL queries. 2. Weaponization: The attacker crafts a malicious SQL query with nested parentheses or CASE WHEN chains. 3. Delivery & Exploitation: The attacker sends the malicious SQL query to the vulnerable application. 4. Post-Exploitation: The parser spends multiple seconds of CPU before the depth cap raises a `SQLParseError`, causing a denial of service. 5. Impact Realization: The vulnerable application is unable to process legitimate requests, leading to a denial of service.

Impact Analysis

Direct Impact

The vulnerability can cause a CPU Denial of Service (DoS) attack, leading to a denial of service. The vulnerability has a high severity score and can be exploited remotely without authentication.

Downstream & Cascading Effects

The vulnerability can have downstream and cascading effects, including: * Denial of service: The vulnerable application may become unresponsive or crash. * Data loss: The vulnerable application may lose unsaved data. * Reputation damage: The vulnerable application may suffer reputational damage due to the denial of service.

Affected Products & Versions

The vulnerability affects all versions of sqlparse, including the latest version 0.5.5.

Detection & Threat Hunting

Indicators of Compromise

The following indicators of compromise can be used to detect the vulnerability: * Unusual CPU usage patterns. * Slow response times from the vulnerable application. * Error messages indicating a denial of service.

Detection Rules & Signatures

The following detection rules and signatures can be used to detect the vulnerability: * Monitor CPU usage patterns for unusual activity. * Monitor response times from the vulnerable application. * Monitor error messages for indications of a denial of service.

Remediation & Hardening

Immediate Actions (0-24 hours)

The following immediate actions can be taken to remediate the vulnerability: * Upgrade to a patched version of sqlparse. * Implement rate limiting on SQL queries. * Monitor CPU usage patterns and response times from the vulnerable application.

Short-Term Hardening (1-7 days)

The following short-term hardening measures can be taken: * Implement additional security controls, such as Web Application Firewalls (WAFs). * Monitor error messages for indications of a denial of service.

Strategic Recommendations

The following strategic recommendations can be made: * Regularly update and patch the sqlparse library. * Implement robust security controls, such as rate limiting and Web Application Firewalls (WAFs). * Monitor CPU usage patterns and response times from the vulnerable application.

Analyst Assessment

The vulnerability has a high severity score and can be exploited remotely without authentication. The vulnerability can cause a CPU Denial of Service (DoS) attack, leading to a denial of service. The vulnerability affects all versions of sqlparse, including the latest version 0.5.5. It is recommended that organizations upgrade to a patched version of sqlparse and implement additional security controls to prevent exploitation.