CVE-2020-7760 Overview
CVE-2020-7760 is a Regular Expression Denial of Service (ReDoS) vulnerability affecting CodeMirror, a popular browser-based text editor component, before version 5.58.2. The vulnerability also affects the org.apache.marmotta.webjars:codemirror package. A maliciously crafted input can exploit a vulnerable regular expression pattern in the JavaScript mode parser, causing catastrophic backtracking that leads to excessive CPU consumption and application unresponsiveness.
Critical Impact
An attacker can remotely trigger denial of service conditions by providing specially crafted JavaScript code to applications using vulnerable CodeMirror instances, potentially rendering web applications unusable.
Affected Products
- CodeMirror versions before 5.58.2
- Oracle Application Express
- Oracle Enterprise Manager Express User Interface 19c
- Oracle Essbase 21.2
- Oracle Hyperion Data Relationship Management
- Oracle Spatial Studio
Discovery Timeline
- October 30, 2020 - CVE-2020-7760 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2020-7760
Vulnerability Analysis
This vulnerability is classified as CWE-400 (Uncontrolled Resource Consumption). The flaw exists in the JavaScript mode syntax highlighting module of CodeMirror, specifically in the regular expression used to parse JavaScript code. The vulnerable regex pattern contains a sub-pattern (s|/*.*?*/)* that is susceptible to catastrophic backtracking when processing certain input strings.
When a user provides malformed JavaScript code containing specific character sequences, the regex engine enters an exponential time complexity state. This occurs because the pattern allows for multiple overlapping match possibilities, causing the engine to explore an enormous number of potential matches before failing.
The vulnerability is exploitable over the network without authentication, as any web application using CodeMirror for code editing or display could be targeted. An attacker simply needs to submit crafted input to the CodeMirror editor component.
Root Cause
The root cause lies in the inefficient regular expression design within the JavaScript mode parser located in mode/javascript/javascript.js. The problematic regex pattern (s|/*.*?*/)* exhibits polynomial or exponential time complexity due to:
- Nested quantifiers: The combination of * and ? within a repeated group creates ambiguous matching paths
- Overlapping alternatives: The alternation between whitespace (s) and comment patterns allows multiple ways to match the same input
- Greedy backtracking: When the regex fails to match, the engine backtracks through all possible combinations, leading to exponential time growth
Attack Vector
The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:
- Identifying a web application that uses a vulnerable version of CodeMirror
- Crafting malicious input strings designed to trigger catastrophic regex backtracking
- Submitting the crafted input through any interface that processes it with CodeMirror's JavaScript mode
- The server or client processing the input will experience CPU exhaustion, leading to denial of service
The attack is particularly effective against applications that perform server-side syntax highlighting or validation using CodeMirror's JavaScript mode.
Detection Methods for CVE-2020-7760
Indicators of Compromise
- Abnormally high CPU utilization on web servers or client browsers during code editing operations
- Unresponsive web application interfaces when processing JavaScript content
- Increased response times or timeouts when submitting code to applications using CodeMirror
- Memory pressure on systems processing syntax highlighting requests
Detection Strategies
- Implement application performance monitoring to detect anomalous CPU spikes during code processing operations
- Monitor web application response times for degradation patterns indicative of ReDoS attacks
- Scan dependencies using software composition analysis (SCA) tools to identify vulnerable CodeMirror versions
- Review JavaScript dependencies in package.json or Maven pom.xml files for CodeMirror versions below 5.58.2
Monitoring Recommendations
- Deploy runtime application self-protection (RASP) solutions to detect regex-based denial of service patterns
- Configure alerts for sustained high CPU usage correlated with code editor functionality
- Implement request timeout thresholds to prevent long-running regex operations from consuming resources
- Monitor for patterns of repeated malformed JavaScript submissions from single sources
How to Mitigate CVE-2020-7760
Immediate Actions Required
- Upgrade CodeMirror to version 5.58.2 or later immediately
- Review all applications and dependencies that may include CodeMirror as a transitive dependency
- Apply Oracle security patches for affected Oracle products (Application Express, Enterprise Manager, Essbase, Hyperion, Spatial Studio)
- Implement input length limits on code editor fields as a temporary mitigation
Patch Information
CodeMirror has released a fix in version 5.58.2 that addresses the vulnerable regular expression pattern. The security fix is available via the GitHub Commit.
For Oracle products, apply the relevant security patches from:
Additional vulnerability details are available from Snyk JS Vulnerability #1016937 and Debian Security Advisory DSA-4789.
Workarounds
- Implement server-side request timeouts to terminate long-running regex operations
- Add input validation to reject excessively long or malformed JavaScript code before processing
- Consider disabling JavaScript mode in CodeMirror if not required for application functionality
- Deploy web application firewalls (WAF) with rules to detect and block ReDoS attack patterns
# Update CodeMirror via npm
npm update codemirror@^5.58.2
# Or specify exact version in package.json
npm install codemirror@5.58.2 --save
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
