CVE-2013-2877 in HTTP Server
Summary
by MITRE
parser.c in libxml2 before 2.9.0, as used in Google Chrome before 28.0.1500.71 and other products, allows remote attackers to cause a denial of service (out-of-bounds read) via a document that ends abruptly, related to the lack of certain checks for the XML_PARSER_EOF state.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 03/02/2022
The vulnerability described in CVE-2013-2877 represents a critical out-of-bounds read flaw within the libxml2 library's XML parser implementation. This issue affects versions prior to 2.9.0 and specifically impacts Google Chrome versions before 28.0.1500.71, along with numerous other software products that rely on libxml2 for XML processing. The vulnerability stems from inadequate validation mechanisms within the parser's handling of XML documents that terminate unexpectedly or abruptly, creating a scenario where the parser fails to properly check for the XML_PARSER_EOF state before attempting to access memory locations beyond the document boundaries.
The technical flaw manifests when the XML parser encounters a document that ends without proper termination sequences or when processing malformed XML content that does not conform to standard XML syntax. During parsing operations, the parser maintains internal state variables to track document progress and memory allocation. When reaching the end of a document, the parser should transition to the XML_PARSER_EOF state and cease further memory access attempts. However, in vulnerable versions of libxml2, this state check is bypassed or inadequately implemented, allowing the parser to continue reading beyond the allocated document memory space. This results in an out-of-bounds memory read condition that can trigger segmentation faults, application crashes, or potentially more severe consequences depending on the execution environment and memory layout.
The operational impact of this vulnerability extends beyond simple denial of service, as it creates potential vectors for more sophisticated attacks. An attacker could craft malicious XML documents designed to trigger the out-of-bounds read condition, leading to application instability and potential system compromise. The vulnerability particularly affects web browsers and applications that process untrusted XML content, making it a significant concern for web-based exploitation. From a cybersecurity perspective, this flaw aligns with CWE-125, which describes out-of-bounds read conditions, and can be mapped to ATT&CK technique T1203, which involves exploiting input validation flaws to cause application instability. The vulnerability's exploitation potential increases when combined with other memory corruption issues, as it can serve as a stepping stone for more advanced attack vectors.
Mitigation strategies for CVE-2013-2877 primarily involve upgrading to libxml2 version 2.9.0 or later, where the parser's EOF state handling has been properly implemented and validated. System administrators should prioritize patching affected applications, particularly web browsers and server software that utilize libxml2 for XML processing. Additional protective measures include implementing strict input validation for XML content, deploying web application firewalls to filter suspicious XML requests, and configuring applications to limit XML document sizes and processing time. Security monitoring should focus on detecting unusual application crashes or memory access patterns that may indicate exploitation attempts. Organizations should also consider implementing sandboxing mechanisms for XML processing operations and maintaining up-to-date vulnerability assessments to identify other potential weaknesses in their XML processing pipelines. The fix implemented in libxml2 2.9.0 specifically addresses the missing EOF state checks and ensures proper boundary validation during document parsing operations, thereby eliminating the root cause of the out-of-bounds read condition.