CVE-2008-4225 in libxml
Summary
by MITRE
Integer overflow in the xmlBufferResize function in libxml2 2.7.2 allows context-dependent attackers to cause a denial of service (infinite loop) via a large XML document.
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Analysis
by VulDB Data Team • 08/21/2019
The vulnerability identified as CVE-2008-4225 represents a critical integer overflow flaw within the libxml2 library version 2.7.2, specifically affecting the xmlBufferResize function. This issue arises from improper handling of buffer size calculations during XML document processing, creating a scenario where maliciously crafted XML content can trigger unexpected behavior in applications relying on this widely-used XML parsing library. The vulnerability exists at the intersection of memory management and input validation, making it particularly dangerous as it can be exploited through context-dependent attack vectors that manipulate XML document structures.
The technical implementation of this vulnerability stems from an integer overflow condition within the xmlBufferResize function where the library attempts to resize internal buffers to accommodate large XML documents. When processing malformed XML data containing excessively large size parameters, the integer arithmetic used for buffer calculations can overflow, resulting in a buffer size that is significantly smaller than the intended allocation. This overflow condition causes the library to enter an infinite loop during buffer reallocation attempts, as the calculated buffer size becomes negative or zero, leading to continuous retry attempts without proper termination conditions. The flaw is categorized under CWE-190 as an integer overflow vulnerability, specifically manifesting as an integer underflow or wraparound condition that affects memory allocation operations.
The operational impact of CVE-2008-4225 extends beyond simple denial of service conditions, as it can be leveraged by context-dependent attackers to disrupt services that depend on libxml2 for XML processing. Applications such as web servers, XML-based web services, content management systems, and various enterprise software platforms that utilize libxml2 for parsing XML data become vulnerable to this attack vector. The infinite loop condition consumes excessive CPU resources and can lead to system instability, making it particularly dangerous in high-availability environments where continuous service availability is critical. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion, and demonstrates how seemingly benign input processing can be weaponized to compromise system availability.
Mitigation strategies for this vulnerability require immediate patching of affected libxml2 installations to versions that address the integer overflow condition in the xmlBufferResize function. System administrators should prioritize updating all applications and services that rely on libxml2, particularly those handling untrusted XML input from external sources. Additional protective measures include implementing XML input validation and size limiting mechanisms, deploying web application firewalls that can detect and block malformed XML content, and establishing monitoring protocols to identify unusual CPU usage patterns that may indicate exploitation attempts. Organizations should also consider implementing input sanitization routines that preprocess XML data to prevent maliciously large buffer size parameters from reaching the vulnerable library functions, thereby reducing the attack surface and providing defense in depth against similar vulnerabilities.