CVE-2012-6128 in OpenConnect
Summary
by MITRE
Multiple stack-based buffer overflows in http.c in OpenConnect before 4.08 allow remote VPN gateways to cause a denial of service (application crash) via a long (1) hostname, (2) path, or (3) cookie list in a response.
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Analysis
by VulDB Data Team • 12/29/2024
The vulnerability identified as CVE-2012-6128 represents a critical stack-based buffer overflow flaw within the OpenConnect VPN client software version 4.07 and earlier. This vulnerability resides in the http.c component of the application, specifically affecting how the software processes network responses from VPN gateways. The flaw manifests when the application receives malformed HTTP responses containing excessively long hostname, path, or cookie list data, creating conditions that can lead to memory corruption and subsequent application instability.
The technical implementation of this vulnerability stems from inadequate input validation within the OpenConnect client's HTTP parsing routines. When processing responses from remote VPN gateways, the software fails to properly bounds-check the length of hostname, path, or cookie list parameters before copying them into fixed-size stack buffers. This fundamental flaw allows attackers positioned on the network to craft malicious HTTP responses that exceed the allocated buffer space, causing stack corruption and triggering application crashes. The vulnerability operates at the network protocol level, making it particularly dangerous as it can be exploited through legitimate network traffic without requiring authentication or privileged access.
The operational impact of CVE-2012-6128 extends beyond simple denial of service, as it creates opportunities for more sophisticated attacks within the context of VPN security. When the application crashes due to buffer overflow conditions, it can lead to complete service disruption for legitimate users attempting to establish secure connections. The vulnerability's exploitation is particularly concerning because it can be triggered by remote attackers who do not need to be physically present or authenticated to the network. This makes it a significant threat in environments where VPN gateways may be exposed to untrusted network traffic or where attackers can perform man-in-the-middle attacks to manipulate HTTP responses.
From a cybersecurity perspective, this vulnerability aligns with CWE-121 Stack-based Buffer Overflow, which specifically addresses situations where data is copied into a stack buffer without proper bounds checking, leading to memory corruption. The attack vector follows patterns consistent with ATT&CK technique T1071.004 Application Layer Protocol: DNS, where network protocols are manipulated to cause application failures. Organizations using OpenConnect VPN clients prior to version 4.08 face significant risk of service disruption and potential exploitation for more advanced attacks if proper network segmentation and monitoring are not implemented. The vulnerability demonstrates the importance of input validation and bounds checking in network protocol implementations, particularly in security-critical applications like VPN clients that handle untrusted network data from remote servers.
The recommended mitigation strategy involves immediate deployment of OpenConnect version 4.08 or later, which includes proper bounds checking and input validation fixes for the affected http.c component. Network administrators should also implement additional monitoring to detect unusual patterns in VPN gateway communications and consider network segmentation to limit exposure to potentially malicious HTTP responses. Regular security assessments of VPN infrastructure and proactive patch management are essential to prevent exploitation of similar vulnerabilities in other network security tools. Organizations should also review their incident response procedures to ensure rapid detection and remediation of any potential exploitation attempts targeting this vulnerability.