CVE-2008-3443 in Ruby
Summary
by MITRE
The regular expression engine (regex.c) in Ruby 1.8.5 and earlier, 1.8.6 through 1.8.6-p286, 1.8.7 through 1.8.7-p71, and 1.9 through r18423 allows remote attackers to cause a denial of service (infinite loop and crash) via multiple long requests to a Ruby socket, related to memory allocation failure, and as demonstrated against Webrick.
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Analysis
by VulDB Data Team • 11/03/2024
The vulnerability identified as CVE-2008-3443 represents a critical denial of service weakness in Ruby's regular expression engine that affects multiple versions of the Ruby programming language. This flaw specifically resides in the regex.c file within the Ruby interpreter, where the regular expression processing logic fails to properly handle certain malformed input patterns. The vulnerability manifests when attackers submit multiple long requests to Ruby socket applications, particularly those utilizing the Webrick web server framework. The issue stems from the engine's inadequate memory allocation handling during complex regular expression evaluations, creating conditions where the processing can enter infinite loops or cause application crashes. This vulnerability directly impacts the availability of Ruby applications by allowing remote attackers to consume excessive system resources through carefully crafted malicious input patterns.
The technical implementation of this vulnerability exploits weaknesses in Ruby's regular expression engine's backtracking algorithm and memory management mechanisms. When processing certain regular expressions with specific patterns, the engine enters a state where it repeatedly attempts to match against input data without proper termination conditions. The flaw is particularly dangerous because it can be triggered through network-based socket connections, making it exploitable from remote locations without requiring local system access. The memory allocation failure occurs during the regular expression compilation and matching phases, where the engine attempts to allocate memory for backtracking states but fails to properly manage these allocations under stress conditions. This creates a resource exhaustion scenario where system memory becomes consumed rapidly, leading to application instability and complete service disruption.
From an operational perspective, this vulnerability poses significant risks to Ruby-based web applications and services that utilize regular expressions for input validation or pattern matching. The attack vector through socket connections means that any Ruby application accepting user input through network interfaces becomes potentially vulnerable, including web applications, API endpoints, and server-side processing services. The impact extends beyond simple service disruption to potentially affecting system stability and availability, particularly in environments where multiple concurrent connections are processed. The vulnerability's exploitation demonstrates the broader category of resource exhaustion attacks that fall under the ATT&CK framework's privilege escalation and denial of service tactics. Organizations running Ruby applications in production environments are particularly at risk since the vulnerability affects widely used versions of the language, and the attack can be executed with minimal technical expertise.
Mitigation strategies for CVE-2008-3443 require immediate action to update affected Ruby installations to patched versions that address the regular expression engine's memory allocation issues. System administrators should prioritize updating Ruby to versions 1.8.7-p72 or later, or 1.9.0 or later, depending on their application requirements. Additionally, implementing input validation and limiting the length of regular expressions processed by applications can help reduce the attack surface. Network-level protections such as rate limiting and connection throttling can provide additional defense-in-depth measures to prevent exploitation attempts. The vulnerability also highlights the importance of proper resource management in interpreted languages and aligns with CWE-129 which addresses improper handling of regular expressions and memory allocation failures. Organizations should conduct comprehensive vulnerability assessments to identify all Ruby applications that may be affected and implement monitoring to detect potential exploitation attempts. This vulnerability serves as a reminder of the critical importance of regular security updates and proper input validation in preventing denial of service attacks that target fundamental language components.