CVE-2023-26364: Adobe Css-tools DOS Vulnerability

CVE-2023-26364 Overview

CVE-2023-26364 is an Improper Input Validation vulnerability affecting the @adobe/css-tools npm package. This vulnerability allows attackers to cause a denial of service condition by providing specially crafted CSS input that triggers parsing failures. The vulnerability can be exploited remotely without requiring user interaction or privileges, making it accessible to unauthenticated attackers.

Critical Impact

Applications using vulnerable versions of @adobe/css-tools may experience service disruption when processing maliciously crafted CSS content.

Affected Products

• Adobe css-tools version 4.3.0 and earlier
• Node.js applications using @adobe/css-tools package
• Build pipelines and CSS processing workflows utilizing the vulnerable package

Discovery Timeline

• 2023-11-17 - CVE-2023-26364 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-26364

Vulnerability Analysis

This vulnerability is classified as CWE-20 (Improper Input Validation), indicating that the CSS parsing functionality fails to properly validate or sanitize input before processing. When the parser encounters specially crafted CSS content, it enters a state that causes degraded performance or failure, resulting in a denial of service condition.

The attack can be executed over the network without requiring any user interaction or authentication. While the impact is limited to availability (no confidentiality or integrity breach), the ease of exploitation makes this vulnerability notable for applications that process untrusted CSS content.

Root Cause

The root cause lies in insufficient input validation within the CSS parsing logic of the @adobe/css-tools library. The parser does not adequately handle edge cases or malformed CSS structures, allowing attackers to craft input that triggers resource exhaustion or parsing errors.

Attack Vector

The vulnerability is exploitable via network-based attack vectors. An attacker can supply malicious CSS content to any application endpoint that processes CSS using the vulnerable library. This could include:

• Web applications accepting user-supplied stylesheets
• Build systems processing CSS from external sources
• Content management systems with CSS customization features

The vulnerability mechanism involves providing malformed CSS input to the parsing functions. According to the GitHub Security Advisory, the parser fails to properly handle certain CSS constructs, leading to denial of service during parsing operations. Applications processing untrusted CSS input are at risk of service disruption.

Detection Methods for CVE-2023-26364

Indicators of Compromise

• Unexpected application crashes or hangs during CSS processing operations
• Elevated resource consumption (CPU/memory) when parsing CSS content
• Error logs showing CSS parsing failures with unusual input patterns
• Service degradation correlating with CSS file uploads or style processing

Detection Strategies

• Monitor application logs for repeated CSS parsing errors or timeouts
• Implement dependency scanning to identify @adobe/css-tools versions prior to 4.3.1
• Use Software Composition Analysis (SCA) tools to track vulnerable npm packages
• Set up alerts for unusual resource consumption patterns in CSS processing services

Monitoring Recommendations

• Enable detailed logging for CSS parsing operations in production environments
• Configure application performance monitoring to detect parsing latency anomalies
• Implement rate limiting on endpoints that accept CSS input
• Use npm audit or similar tools in CI/CD pipelines to detect vulnerable dependencies

How to Mitigate CVE-2023-26364

Immediate Actions Required

• Audit your application dependencies to identify usage of @adobe/css-tools version 4.3.0 or earlier
• Update the @adobe/css-tools package to a patched version
• Review and restrict endpoints that accept CSS input from untrusted sources
• Implement input size limits and timeouts for CSS parsing operations

Patch Information

Adobe has addressed this vulnerability in the css-tools package. Review the GitHub Security Advisory for specific patch information and upgrade instructions. Users should update to a version newer than 4.3.0 to remediate this vulnerability.

Workarounds

• Implement input validation and sanitization before passing CSS to the parser
• Set processing timeouts to prevent extended resource consumption
• Restrict CSS input sources to trusted origins only
• Consider using alternative CSS parsing libraries if immediate upgrade is not possible

# Update @adobe/css-tools to latest version
npm update @adobe/css-tools

# Or specify minimum version in package.json
npm install @adobe/css-tools@latest

# Verify installed version
npm list @adobe/css-tools