CVE-2024-34459 in xmllint
Summary
by MITRE • 05/14/2024
An issue was discovered in xmllint (from libxml2) before 2.11.8 and 2.12.x before 2.12.7. Formatting error messages with xmllint --htmlout can result in a buffer over-read in xmlHTMLPrintFileContext in xmllint.c.
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Analysis
by VulDB Data Team • 05/28/2026
The vulnerability identified as CVE-2024-34459 represents a critical buffer over-read flaw within the xmllint utility, which is part of the libxml2 library ecosystem. This issue specifically affects versions prior to 2.11.8 and 2.12.x before 2.12.7, creating a potential exploitation vector for attackers who can manipulate XML input processed through the HTML output formatting functionality. The flaw manifests when the xmllint utility processes malformed HTML content using the --htmlout flag, which triggers a memory access violation that could lead to system instability or information disclosure.
The technical root cause of this vulnerability lies in the xmlHTMLPrintFileContext function within the xmllint.c source file, where improper bounds checking occurs during the formatting of error messages. When xmllint encounters malformed HTML input and attempts to generate error output using the --htmlout option, the buffer over-read occurs due to insufficient validation of input boundaries before memory access operations. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, though in this specific case the over-read occurs in heap memory management rather than traditional stack overflow scenarios. The flaw represents a classic example of improper input validation where the application fails to properly constrain memory access operations based on the actual size of input data.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions, as it could potentially enable attackers to extract sensitive information from memory through careful exploitation of the buffer over-read behavior. When an attacker can control the input to xmllint with --htmlout flag, they may be able to craft malicious HTML content that triggers the vulnerable code path, potentially leading to information disclosure or even remote code execution depending on the system configuration and memory layout. This vulnerability is particularly concerning in environments where xmllint is used to process untrusted XML or HTML content from external sources, as it creates a potential attack surface for privilege escalation or data exfiltration scenarios. The ATT&CK framework would categorize this as a technique involving input validation and memory corruption, potentially leading to privilege escalation or information gathering activities.
Mitigation strategies for CVE-2024-34459 should prioritize immediate patching of affected libxml2 installations to versions 2.11.8 or 2.12.7 and later, which contain the necessary code fixes to prevent the buffer over-read condition. Organizations should also implement input validation measures that restrict the use of the --htmlout flag in environments where untrusted input is processed, and consider deploying additional monitoring to detect unusual memory access patterns or error message generation that might indicate exploitation attempts. System administrators should review all processes that invoke xmllint with HTML output formatting capabilities and ensure that proper access controls and sandboxing measures are in place to limit potential damage from successful exploitation attempts. The vulnerability demonstrates the critical importance of maintaining up-to-date security patches and proper input validation in XML processing utilities, as even seemingly benign command-line tools can present significant security risks when not properly maintained.