CVE-2011-2900 in shttpd
Summary
by MITRE
Stack-based buffer overflow in the (1) put_dir function in mongoose.c in Mongoose 3.0, (2) put_dir function in yasslEWS.c in yaSSL Embedded Web Server (yasslEWS) 0.2, and (3) _shttpd_put_dir function in io_dir.c in Simple HTTPD (shttpd) 1.42 allows remote attackers to execute arbitrary code via an HTTP PUT request, as exploited in the wild in 2011.
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Analysis
by VulDB Data Team • 07/16/2024
The vulnerability identified as CVE-2011-2900 represents a critical stack-based buffer overflow affecting three distinct web server implementations including Mongoose 3.0, yaSSL Embedded Web Server 0.2, and Simple HTTPD 1.42. This flaw exists within the directory handling functions of these web servers, specifically the put_dir function in mongoose.c, the put_dir function in yasslEWS.c, and the _shttpd_put_dir function in io_dir.c. The vulnerability enables remote code execution through specially crafted HTTP PUT requests that exploit the improper bounds checking in directory creation operations. The attack vector is particularly dangerous as it allows adversaries to execute arbitrary code on vulnerable systems without requiring authentication, making it a significant threat to web server security. The exploitation occurred in the wild during 2011, demonstrating the real-world impact and urgency of addressing this vulnerability across affected implementations.
The technical nature of this flaw stems from insufficient input validation and buffer management within the HTTP PUT request processing logic. When these web servers receive an HTTP PUT request containing directory creation commands, the implementations fail to properly validate the length of input data before copying it into fixed-size stack buffers. This classic buffer overflow condition occurs because the code does not check whether the incoming directory path data exceeds the allocated buffer space, allowing attackers to overwrite adjacent stack memory. The vulnerability manifests as a stack-based buffer overflow because the affected functions use stack-allocated buffers that are insufficiently sized to handle potentially malicious input. According to CWE standards, this maps to CWE-121 which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite stack memory. The flaw directly relates to the ATT&CK technique T1190 which involves exploiting vulnerabilities in web applications to execute arbitrary code.
The operational impact of CVE-2011-2900 extends far beyond simple code execution, as it provides attackers with complete system compromise capabilities. Once successfully exploited, adversaries can gain full control over vulnerable web servers, potentially leading to data breaches, service disruption, and lateral movement within networks. The vulnerability affects web servers that handle file uploads through HTTP PUT requests, making it particularly dangerous for applications that allow user file uploads or web-based content management. The widespread exploitation in 2011 indicates that this vulnerability was actively targeted by attackers, with many affected systems likely compromised. Organizations running these specific web server implementations faced significant risk exposure, as the vulnerability could be exploited without any authentication requirements, making it a prime target for automated attacks and botnets. The security implications extend to potential denial of service conditions, data corruption, and complete system takeover scenarios.
Mitigation strategies for CVE-2011-2900 require immediate action from affected organizations to patch or upgrade their web server implementations. The primary remediation involves updating to patched versions of Mongoose, yaSSL Embedded Web Server, or Simple HTTPD that contain proper bounds checking and input validation for directory operations. Organizations should also implement network segmentation and access controls to limit exposure to vulnerable web servers, particularly those handling HTTP PUT requests. Input validation should be enhanced at multiple levels including application firewalls, web application firewalls, and direct server-side validation to prevent malicious directory paths from reaching the vulnerable functions. Additionally, organizations should disable HTTP PUT methods where possible, as this vulnerability specifically exploits PUT request handling capabilities. Security monitoring should include detection of unusual HTTP PUT request patterns and directory creation operations that might indicate exploitation attempts. Regular vulnerability assessments and penetration testing should be conducted to identify similar buffer overflow conditions in other web server components and ensure comprehensive security coverage. The remediation process should also include thorough testing of patched implementations to ensure that security updates do not introduce regressions in functionality while maintaining the intended security protections.