CVE-2011-4315 in nginx
Summary
by MITRE
Heap-based buffer overflow in compression-pointer processing in core/ngx_resolver.c in nginx before 1.0.10 allows remote resolvers to cause a denial of service (daemon crash) or possibly have unspecified other impact via a long response.
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Analysis
by VulDB Data Team • 01/05/2025
The vulnerability described in CVE-2011-4315 represents a critical heap-based buffer overflow affecting the nginx web server's DNS resolver functionality. This flaw exists within the core/ngx_resolver.c file and specifically impacts the processing of compression pointers during DNS resolution operations. The issue arises when nginx receives DNS responses containing excessively long compression pointers, which causes the application to attempt to write data beyond the allocated heap memory boundaries. Such buffer overflows typically occur when input validation is insufficient and the software assumes fixed-size buffers without proper bounds checking.
The technical implementation of this vulnerability stems from nginx's handling of DNS compression pointers, which are used to reduce DNS message size by referencing previously transmitted strings. When a remote DNS resolver sends a malformed response containing an oversized compression pointer, the nginx resolver module fails to properly validate the pointer length before attempting to process it. This processing occurs in the context of the nginx daemon itself, making the impact particularly severe as it can trigger immediate daemon crashes. The vulnerability affects nginx versions prior to 1.0.10, indicating that this was a known issue that required patching to address the memory corruption behavior.
From an operational perspective, this vulnerability creates significant risk for nginx deployments as it can be exploited remotely without authentication, making it particularly dangerous in production environments. The potential impacts extend beyond simple denial of service to include possible code execution or arbitrary code execution in certain configurations, though the primary vector described focuses on daemon crashes. The vulnerability's remote exploitability means that attackers can target nginx servers simply by sending specially crafted DNS responses to the resolver, making it a high-severity threat that can be exploited at scale. Organizations running affected nginx versions face immediate risk of service disruption and potential system compromise.
The mitigation strategy for CVE-2011-4315 involves upgrading to nginx version 1.0.10 or later, which contains the necessary patches to address the buffer overflow in DNS resolver processing. Additionally, network administrators should implement proper DNS resolver configuration practices, including limiting the number of DNS queries and implementing proper input validation for DNS responses. Organizations should also consider implementing network segmentation and monitoring to detect anomalous DNS traffic patterns that might indicate exploitation attempts. This vulnerability aligns with CWE-121, heap-based buffer overflow, and maps to ATT&CK technique T1071.004 for application layer protocol usage, particularly in DNS resolution contexts. The fix implemented in nginx 1.0.10 demonstrates proper bounds checking and input validation for compression pointer processing, preventing the heap corruption that previously enabled the vulnerability.