CVE-2015-3281 in HAProxy
Summary
by MITRE
The buffer_slow_realign function in HAProxy 1.5.x before 1.5.14 and 1.6-dev does not properly realign a buffer that is used for pending outgoing data, which allows remote attackers to obtain sensitive information (uninitialized memory contents of previous requests) via a crafted request.
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Analysis
by VulDB Data Team • 11/25/2024
The vulnerability identified as CVE-2015-3281 affects HAProxy versions 1.5.x before 1.5.14 and 1.6-dev, representing a critical security flaw in the load balancing and proxying software widely deployed in enterprise environments. This issue resides within the buffer_slow_realign function, which is responsible for managing memory buffers used to handle pending outgoing data. The flaw manifests when the function fails to properly realign memory buffers, creating a condition where uninitialized memory contents from previous requests persist in the buffer space. This behavior directly violates fundamental security principles of memory management and data isolation, as sensitive information from one request can leak into subsequent responses. The vulnerability classifies under CWE-128, which addresses "Wrap or Overflow" conditions in memory operations, specifically involving buffer management failures that can lead to information disclosure.
The operational impact of this vulnerability is severe and multifaceted, particularly in environments where HAProxy serves as a critical component for web application delivery and SSL termination. Remote attackers can exploit this flaw by crafting specially designed requests that trigger the buffer realignment process, thereby accessing uninitialized memory segments that may contain sensitive data from previous connections. This includes potentially confidential information such as session tokens, user credentials, database connection details, or other application-specific data that was previously processed by the same memory buffers. The vulnerability demonstrates characteristics aligned with ATT&CK technique T1005, which involves data from local system collection, as it enables unauthorized access to memory contents that should remain isolated between different request contexts. The attack vector is particularly concerning because it requires no authentication and can be executed over the network, making it suitable for automated exploitation at scale.
The technical implementation of this vulnerability stems from improper buffer management within HAProxy's internal memory handling mechanisms. When the buffer_slow_realign function processes data, it does not adequately zero out or properly initialize memory segments before reuse, allowing previous data to remain accessible. This memory corruption issue creates a persistent information leak that can accumulate over time, with each subsequent request potentially exposing more sensitive data from previous connections. The vulnerability affects the core functionality of HAProxy's data processing pipeline, specifically in scenarios involving long-running connections or high-volume request processing where buffer reallocation occurs frequently. Security practitioners should note that this vulnerability can be particularly dangerous in environments with sensitive data handling, such as financial services, healthcare applications, or government systems where information disclosure can lead to significant compliance violations and data breaches. The flaw highlights the importance of proper memory management practices and the necessity of thorough code review processes for security-critical components, particularly those handling sensitive data in network proxy applications.
Mitigation strategies for CVE-2015-3281 should prioritize immediate patching of affected HAProxy versions to 1.5.14 or later releases, which contain the necessary fixes for buffer realignment operations. Organizations should implement network segmentation and access controls to limit exposure of vulnerable HAProxy instances, particularly those handling sensitive data. Regular security assessments and memory analysis should be conducted to detect potential exploitation attempts. Additionally, implementing monitoring solutions that can detect unusual patterns of data access or memory usage may help identify exploitation attempts. System administrators should also consider deploying intrusion detection systems that can flag suspicious traffic patterns consistent with this vulnerability. The fix implemented in patched versions addresses the root cause by ensuring proper buffer initialization and realignment procedures, preventing the leakage of uninitialized memory contents. Organizations should conduct comprehensive testing of patched environments to ensure that the security fix does not introduce performance regressions or compatibility issues with existing configurations.