CVE-2014-4049 in Mac OS X
Summary
by MITRE
Heap-based buffer overflow in the php_parserr function in ext/standard/dns.c in PHP 5.6.0beta4 and earlier allows remote servers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted DNS TXT record, related to the dns_get_record function.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 02/20/2022
The vulnerability CVE-2014-4049 represents a critical heap-based buffer overflow in PHP's DNS parsing functionality that affects versions 5.6.0beta4 and earlier. This flaw resides within the php_parserr function located in the ext/standard/dns.c file, which is responsible for processing DNS records during DNS resolution operations. The vulnerability specifically impacts the dns_get_record function, which is commonly used by web applications to query DNS information and retrieve various types of DNS records including TXT records.
The technical implementation of this vulnerability stems from insufficient bounds checking when processing DNS TXT records. When PHP encounters a malformed or crafted DNS TXT record, the php_parserr function fails to properly validate the length of the record data before copying it into heap-allocated memory buffers. This inadequate input validation creates a condition where an attacker can craft a specially formatted DNS TXT record that exceeds the allocated buffer size, resulting in memory corruption. The heap-based nature of the overflow means that the vulnerability can be exploited to overwrite adjacent memory locations, potentially leading to arbitrary code execution or system crashes.
The operational impact of this vulnerability extends beyond simple denial of service to include potential remote code execution capabilities. Attackers can leverage this flaw by controlling a DNS server that responds to queries from vulnerable PHP applications, particularly those that process user input through DNS lookups. The vulnerability affects web applications that utilize the dns_get_record function, making it a significant concern for PHP-based web services, content management systems, and applications that perform DNS resolution for user-provided domains. The exploitability of this vulnerability is enhanced by the fact that many PHP applications perform DNS lookups without proper input sanitization, creating a wide attack surface.
This vulnerability aligns with CWE-121 Heap-based Buffer Overflow, which specifically addresses buffer overflows occurring in heap memory regions. The attack pattern follows the TTPs outlined in the MITRE ATT&CK framework under the technique of "Exploitation for Privilege Escalation" and "Command and Scripting Interpreter" categories. Organizations running vulnerable PHP versions face significant risk as this flaw can be exploited without authentication, making it particularly dangerous in web environments where DNS queries are frequently performed. The vulnerability demonstrates the importance of input validation and memory safety practices in network-facing applications, particularly those handling external data sources like DNS records.
Mitigation strategies for CVE-2014-4049 include immediate patching of PHP installations to versions 5.6.0beta5 or later, where the buffer overflow has been addressed through proper bounds checking. Organizations should also implement DNS query validation and sanitization measures, including limiting DNS resolution to trusted domains and implementing rate limiting for DNS queries. Network segmentation and firewall rules can help reduce exposure by limiting DNS server access to only necessary applications. Additionally, application-level input validation should be strengthened to prevent untrusted DNS data from being processed without proper sanitization. Regular security audits and vulnerability assessments should be conducted to identify similar issues in other network services and applications, ensuring comprehensive protection against similar heap-based buffer overflow vulnerabilities.