CVE-2012-6063 in libssh
Summary
by MITRE
Double free vulnerability in the sftp_mkdir function in sftp.c in libssh before 0.5.3 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via unspecified vectors, a different vector than CVE-2012-4559.
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Analysis
by VulDB Data Team • 12/20/2021
The CVE-2012-6063 vulnerability represents a critical double free condition within the sftp_mkdir function of libssh version 0.5.2 and earlier. This flaw exists in the sftp.c source file where the software fails to properly validate memory allocation states during SFTP directory creation operations. The vulnerability stems from improper handling of memory resources where the same memory block gets freed twice, creating a scenario that can be exploited by remote attackers to manipulate the program's memory management routines.
The technical implementation of this vulnerability occurs when the sftp_mkdir function processes directory creation requests through SFTP protocol communications. When malformed or specially crafted SFTP requests are sent to a vulnerable libssh server, the function executes code paths that lead to the same memory pointer being passed to the free() function twice. This double free condition creates a heap corruption state that can be leveraged for arbitrary code execution or system crash. The vulnerability operates at the memory management level, specifically targeting the heap allocator's behavior when handling freed memory blocks.
From an operational standpoint, this vulnerability presents significant risks to systems utilizing libssh for secure file transfers and remote access operations. Attackers can exploit this flaw to cause immediate system crashes, leading to denial of service conditions that disrupt legitimate user access to SFTP services. The potential for arbitrary code execution adds an additional layer of risk, as compromised systems could be used as stepping stones for further attacks or to establish persistent access. The vulnerability affects any system running libssh versions prior to 0.5.3, making it particularly dangerous in environments where patch management is delayed or incomplete.
The impact of this vulnerability aligns with CWE-415, which describes improper double free conditions in software implementations. This weakness allows attackers to manipulate memory management functions and potentially execute malicious code through heap corruption techniques. The ATT&CK framework categorizes this as a memory corruption vulnerability that can be leveraged for privilege escalation and persistent access within compromised systems. Organizations using libssh should prioritize immediate patching to address this vulnerability, as the attack surface includes any SFTP server implementation that relies on vulnerable versions of the library.
Mitigation strategies for CVE-2012-6063 require immediate deployment of libssh version 0.5.3 or later, which contains the necessary memory management fixes to prevent the double free condition. System administrators should also implement network segmentation and access controls to limit exposure of vulnerable SFTP services to untrusted networks. Additionally, monitoring systems should be configured to detect unusual SFTP traffic patterns that might indicate exploitation attempts. Regular vulnerability assessments and security audits should verify that all instances of libssh are updated to secure versions, and automated patch management systems should be implemented to prevent future exposure to similar memory corruption vulnerabilities. The remediation process should include thorough testing of patched environments to ensure that the fix does not introduce compatibility issues with existing SFTP client applications.