CVE-2011-4000 in ChaSen
Summary
by MITRE
Buffer overflow in ChaSen 2.4.x allows remote attackers to execute arbitrary code via a crafted string.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 11/26/2021
The vulnerability identified as CVE-2011-4000 represents a critical buffer overflow flaw within ChaSen 2.4.x, a Japanese morphological analysis tool widely used for natural language processing tasks. This vulnerability resides in the way the software handles input strings during text processing operations, creating an exploitable condition that can be remotely triggered by malicious actors. The flaw specifically manifests when the application processes specially crafted input data that exceeds the allocated buffer space, leading to potential memory corruption and unauthorized code execution. ChaSen is commonly integrated into various text processing pipelines and applications requiring Japanese language analysis, making this vulnerability particularly concerning for systems handling sensitive data or operating in networked environments. The buffer overflow occurs during the parsing and tokenization of input text, where the software fails to properly validate the length of incoming strings against predetermined buffer limits, allowing attackers to overwrite adjacent memory locations.
The technical implementation of this vulnerability aligns with CWE-121, which describes buffer overflow conditions where insufficient bounds checking allows data to be written beyond the allocated buffer boundaries. The flaw operates through a classic stack-based buffer overflow scenario where a crafted input string causes the program to write beyond the intended memory allocation, potentially overwriting return addresses, function pointers, or other critical program state information. Attackers can exploit this by constructing a malicious input string that, when processed by ChaSen, triggers the buffer overflow condition and redirects execution flow to malicious code. The vulnerability is particularly dangerous because it allows for arbitrary code execution, enabling attackers to gain full control over the affected system or application. This type of vulnerability falls under the ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation would allow adversaries to execute commands on the compromised system. The vulnerability affects all versions of ChaSen 2.4.x and earlier, with the potential for exploitation across different operating systems where the software is deployed, including unix-like systems and windows environments that support the application.
The operational impact of CVE-2011-4000 extends beyond simple code execution to encompass significant security risks for organizations relying on ChaSen for text processing operations. Systems that utilize ChaSen for processing user input, log analysis, or automated text mining operations become vulnerable to remote code execution attacks, potentially allowing adversaries to establish persistent access, escalate privileges, or deploy additional malware. The vulnerability's remote exploitability means that attackers do not require physical access to the system, making it particularly dangerous for web applications or services that process external input through ChaSen. Organizations using ChaSen in production environments may face data breaches, system compromise, or service disruption if this vulnerability remains unpatched. The impact is further amplified by the widespread use of ChaSen in Japanese language processing applications, suggesting that numerous systems across different sectors including finance, healthcare, and government may be at risk. Network administrators and security teams must consider the potential for lateral movement within compromised networks, as successful exploitation could provide attackers with a foothold for further reconnaissance and attack progression.
Mitigation strategies for CVE-2011-4000 should prioritize immediate patching of affected ChaSen installations to address the buffer overflow condition. Organizations should implement input validation measures to prevent malformed strings from reaching the vulnerable parsing functions, including length checking and string sanitization routines. Network segmentation and access controls can help limit the potential impact of exploitation by restricting access to ChaSen-dependent applications. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of the vulnerable software within the organization's infrastructure. The implementation of address space layout randomization and stack canaries may provide additional protection against exploitation attempts, though these are considered defensive measures rather than primary fixes. System monitoring should be enhanced to detect unusual processing patterns or memory access violations that might indicate exploitation attempts. Security teams should also consider implementing intrusion detection systems that can identify malicious input patterns targeting this specific vulnerability. Given the age of the affected software version, organizations should evaluate migrating to more recent, supported versions of morphological analysis tools or implementing additional protective measures such as application whitelisting to prevent execution of vulnerable binaries. The vulnerability serves as a reminder of the importance of maintaining up-to-date software components and implementing comprehensive security practices across all system elements that process external input data.