CVE-2016-5360 in HAProxy
Summary
by MITRE
HAproxy 1.6.x before 1.6.6, when a deny comes from a reqdeny rule, allows remote attackers to cause a denial of service (uninitialized memory access and crash) or possibly have unspecified other impact via unknown vectors.
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Analysis
by VulDB Data Team • 09/27/2024
The vulnerability identified as CVE-2016-5360 affects HAproxy versions 1.6.x prior to 1.6.6 and represents a critical security flaw that manifests when the proxy server processes requests that match a reqdeny rule. This issue falls under the category of uninitialized memory access, a common class of vulnerabilities that can lead to unpredictable behavior and system instability. The vulnerability specifically occurs during the handling of denial requests, where the software fails to properly initialize memory structures before accessing them, creating a potential attack surface for remote adversaries.
The technical flaw stems from improper memory management within HAproxy's request denial mechanism. When a request is matched against a reqdeny rule, the application attempts to process the denial without ensuring that all memory locations have been properly initialized. This uninitialized memory access can result in the software reading garbage data from memory locations, leading to unpredictable program behavior. The vulnerability is particularly dangerous because it can be triggered remotely without requiring authentication, making it an attractive target for attackers seeking to disrupt services. The unspecified other impacts mentioned in the description suggest that beyond simple denial of service, this flaw could potentially enable additional attack vectors or information disclosure scenarios.
The operational impact of this vulnerability is significant for organizations relying on HAproxy as a load balancer or reverse proxy solution. A successful exploitation could result in complete service disruption through application crashes, forcing administrators to restart the proxy service and potentially causing temporary loss of access to backend applications. The remote nature of the attack means that attackers do not need physical access to the system or network privileges to exploit this vulnerability, making it particularly concerning for publicly accessible services. Organizations using vulnerable versions of HAproxy are at risk of experiencing extended downtime during exploitation attempts, which can have cascading effects on business operations and user experience.
From a cybersecurity perspective, this vulnerability aligns with CWE-457, which describes the use of uninitialized variables in software development, and represents a classic example of memory safety issues that have been increasingly targeted in recent years. The ATT&CK framework categorizes this type of vulnerability under the T1499.004 technique for Network Denial of Service, as it enables attackers to disrupt network services through memory corruption. Organizations should prioritize immediate patching of affected systems, as the vulnerability does not require complex exploitation techniques and can be triggered by simple network requests. The remediation process involves upgrading to HAproxy version 1.6.6 or later, which includes proper memory initialization routines that prevent the uninitialized access pattern. Additionally, implementing network segmentation and access controls can help limit the potential impact of such vulnerabilities while patches are deployed, and regular security assessments should verify that all proxy configurations properly handle denial rules without exposing system memory to uninitialized access patterns.