CVE-2012-5134 in iOS
Summary
by MITRE
Heap-based buffer underflow in the xmlParseAttValueComplex function in parser.c in libxml2 2.9.0 and earlier, as used in Google Chrome before 23.0.1271.91 and other products, allows remote attackers to cause a denial of service or possibly execute arbitrary code via crafted entities in an XML document.
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Analysis
by VulDB Data Team • 05/25/2021
The vulnerability identified as CVE-2012-5134 represents a critical heap-based buffer underflow flaw within the libxml2 library's XML parser implementation. This issue specifically affects the xmlParseAttValueComplex function located in the parser.c file, which is part of libxml2 version 2.9.0 and earlier releases. The vulnerability arises from insufficient input validation and memory management when processing XML entities, creating a scenario where maliciously crafted XML documents can trigger memory corruption. The flaw manifests when the parser encounters specially constructed entity references that cause the buffer underflow condition, potentially leading to unpredictable behavior in the affected applications.
The technical exploitation of this vulnerability occurs through the manipulation of XML document structures, particularly when dealing with complex attribute values and entity references. When Google Chrome processes XML content using the vulnerable libxml2 library, the parser fails to properly validate the boundaries of memory allocations during entity value processing. This allows attackers to craft XML documents containing malformed entity declarations that, when parsed, result in memory corruption. The underflow condition can cause the application to access memory locations outside the intended buffer boundaries, leading to either application crashes or potential code execution. The vulnerability's impact is amplified because libxml2 is widely used across numerous applications and browsers, making this a significant threat vector.
The operational impact of CVE-2012-5134 extends beyond simple denial of service scenarios to potentially enable remote code execution in affected systems. When exploited, this vulnerability can cause applications to crash or behave unpredictably, resulting in service disruption for users. More concerning is the potential for arbitrary code execution, which could allow attackers to gain control over affected systems. The vulnerability affects Google Chrome versions prior to 23.0.1271.91, but since libxml2 is integrated into many other software products, the attack surface is extensive. Organizations using affected versions face significant risk as attackers can leverage this vulnerability to compromise user systems through web-based XML content, making it particularly dangerous in enterprise environments where web browsing is prevalent.
Mitigation strategies for this vulnerability primarily focus on immediate software updates and patches to address the root cause within libxml2. System administrators should prioritize updating all affected applications to versions that incorporate patched libxml2 libraries, particularly Google Chrome versions 23.0.1271.91 and later. Organizations should implement network-level protections such as XML filtering and content validation to prevent malformed XML content from reaching vulnerable applications. Additionally, security teams should consider implementing application whitelisting and sandboxing measures to limit the potential impact of successful exploitation attempts. The vulnerability aligns with CWE-121 heap-based buffer overflow classification and may map to ATT&CK techniques involving code injection and privilege escalation through memory corruption vulnerabilities. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of the vulnerable library versions within the organization's infrastructure, ensuring comprehensive protection against similar threats.