CVE-2012-6540 in Linux
Summary
by MITRE
The do_ip_vs_get_ctl function in net/netfilter/ipvs/ip_vs_ctl.c in the Linux kernel before 3.6 does not initialize a certain structure for IP_VS_SO_GET_TIMEOUT commands, which allows local users to obtain sensitive information from kernel stack memory via a crafted application.
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Analysis
by VulDB Data Team • 01/01/2022
The vulnerability identified as CVE-2012-6540 resides within the Linux kernel's IP Virtual Server implementation, specifically in the do_ip_vs_get_ctl function located in net/netfilter/ipvs/ip_vs_ctl.c. This flaw affects Linux kernel versions prior to 3.6 and represents a classic information disclosure vulnerability that exploits improper initialization of kernel data structures. The issue manifests when processing IP_VS_SO_GET_TIMEOUT commands, which are used to retrieve timeout values for IPVS (IP Virtual Server) connections. The vulnerability stems from the function's failure to properly initialize a structure before populating it with data, creating a scenario where uninitialized memory contents are exposed to user-space applications.
The technical nature of this vulnerability aligns with CWE-1288, which deals with improper initialization of structure members, and can be categorized under the broader ATT&CK technique T1005 for data from local system. When a local user crafts a specific application that sends IP_VS_SO_GET_TIMEOUT commands to the kernel, the do_ip_vs_get_ctl function processes this request without properly initializing the target structure. This omission results in sensitive data remnants from kernel stack memory being inadvertently copied into the response buffer and subsequently accessible to the unprivileged user application. The uninitialized memory may contain previously stored kernel data, cryptographic keys, or other sensitive information that was not explicitly cleared before reuse, creating a potential information leakage vector.
The operational impact of CVE-2012-6540 is significant for systems running affected Linux kernel versions, particularly those utilizing IPVS for load balancing or virtual server implementations. While the vulnerability requires local user access, it can be exploited by any user with sufficient privileges to execute applications that interface with the kernel's IPVS subsystem. The information disclosed through this vulnerability could include kernel memory addresses, internal data structures, or other sensitive information that might aid in further exploitation attempts. Although the vulnerability does not directly enable privilege escalation or remote code execution, it provides attackers with valuable insights into the kernel's memory layout and internal state, which can be leveraged in combination with other vulnerabilities to craft more sophisticated attacks.
Mitigation strategies for CVE-2012-6540 primarily focus on kernel version upgrades to 3.6 or later, where the vulnerability has been addressed through proper structure initialization. System administrators should prioritize patching affected systems, particularly those running IPVS services or load balancing configurations. Additionally, implementing proper access controls and monitoring for suspicious kernel interface usage can help detect potential exploitation attempts. The fix implemented in kernel version 3.6 ensures that all structure members are properly initialized before data is copied from kernel space to user space, preventing the leakage of uninitialized memory contents. Organizations should also consider implementing kernel hardening measures such as stack canaries and address space layout randomization to further reduce the attack surface and potential impact of similar vulnerabilities.