CVE-2018-1109 in Braces
Summary
by MITRE • 03/30/2021
A vulnerability was found in Braces versions 2.2.0 and above, prior to 2.3.1. Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) attacks.
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Analysis
by VulDB Data Team • 12/01/2025
The vulnerability identified as CVE-2018-1109 represents a critical security flaw in the Braces library, a popular npm package used for brace expansion in JavaScript applications. This vulnerability specifically affects versions 2.2.0 through 2.3.0, creating a significant risk for developers who rely on this package for pattern matching and string manipulation operations. The Braces library is widely adopted in build tools, task runners, and various Node.js applications, making this vulnerability particularly dangerous as it can affect numerous downstream dependencies and projects.
The technical flaw manifests as a Regular Expression Denial of Service (ReDoS) vulnerability, which occurs when maliciously crafted input causes the regular expression engine to consume excessive computational resources. In the affected Braces versions, the vulnerability stems from poorly constructed regular expressions that exhibit exponential backtracking behavior when processing certain input patterns. This allows an attacker to craft specific inputs that cause the regular expression engine to spend an extraordinarily long time processing, effectively creating a denial of service condition that can crash applications or make them unresponsive. The vulnerability operates at the level of regular expression parsing and execution, making it particularly insidious as it can be triggered through user input or configuration files that are processed by the library.
The operational impact of this vulnerability extends far beyond individual applications, as Braces is a dependency for many popular tools and frameworks within the Node.js ecosystem. When exploited, this vulnerability can cause applications to become unresponsive or crash entirely, leading to service disruption and potential business impact. The vulnerability is particularly concerning because it can be triggered through seemingly innocuous input patterns that appear legitimate to users but contain hidden malicious constructs designed to exploit the regular expression backtracking behavior. This makes it difficult to detect during normal testing procedures and can remain undetected in production environments until actively exploited. The vulnerability affects both server-side applications and client-side code that uses the library, creating a broad attack surface that spans multiple execution contexts.
Mitigation strategies for CVE-2018-1109 primarily involve upgrading to Braces version 2.3.1 or later, which contains the patched regular expressions that eliminate the vulnerable backtracking patterns. Organizations should conduct thorough dependency audits to identify all applications and systems that utilize affected versions of the library and prioritize updating these dependencies as quickly as possible. Additional protective measures include implementing input validation and sanitization at application boundaries to prevent malicious patterns from reaching the vulnerable library code, as well as monitoring for unusual processing times or resource consumption that might indicate exploitation attempts. Security teams should also consider implementing network-level protections such as rate limiting and input filtering to reduce the effectiveness of potential attacks. This vulnerability aligns with CWE-400, which categorizes improper input validation leading to resource exhaustion, and maps to ATT&CK technique T1499.004 for network denial of service attacks. Organizations should also implement automated dependency checking tools to proactively identify and remediate similar vulnerabilities in their software supply chains, as this type of vulnerability demonstrates the importance of maintaining up-to-date dependencies in modern software development practices.