CVE-2016-7134 in PHP
Summary
by MITRE
ext/curl/interface.c in PHP 7.x before 7.0.10 does not work around a libcurl integer overflow, which allows remote attackers to cause a denial of service (allocation error and heap-based buffer overflow) or possibly have unspecified other impact via a long string that is mishandled in a curl_escape call.
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Analysis
by VulDB Data Team • 09/16/2022
The vulnerability identified as CVE-2016-7134 represents a critical integer overflow flaw within PHP 7.x versions prior to 7.0.10, specifically affecting the ext/curl/interface.c module. This issue stems from inadequate handling of integer overflow conditions within the libcurl library integration, creating a dangerous scenario where maliciously crafted input can trigger system instability. The vulnerability manifests through the curl_escape function call, which processes user-supplied strings without proper bounds checking, leading to potential memory corruption and system compromise.
The technical exploitation of this vulnerability occurs when PHP applications utilize the curl_escape function to process excessively long strings. The integer overflow vulnerability arises from the library's inability to properly validate input lengths, allowing attackers to manipulate memory allocation parameters. When a malicious string exceeds the expected integer limits, the system attempts to allocate memory blocks that either exceed available system resources or trigger heap-based buffer overflows. This creates a condition where the application may crash or potentially execute arbitrary code depending on the specific memory corruption patterns. The vulnerability falls under CWE-191, which specifically addresses integer underflow and overflow conditions, and aligns with ATT&CK technique T1499.004 for resource exhaustion attacks.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially enable remote code execution in certain environments. Attackers can leverage this flaw to cause heap corruption, leading to unpredictable application behavior that may be exploited for privilege escalation or system compromise. The vulnerability affects PHP applications that make extensive use of curl functions, particularly those handling untrusted input from web forms, API endpoints, or external data sources. Organizations running PHP 7.x versions before 7.0.10 are at significant risk, as this vulnerability can be triggered through common web application attack vectors such as parameter manipulation or file upload scenarios.
Mitigation strategies for CVE-2016-7134 primarily focus on immediate version updates to PHP 7.0.10 or later releases, which contain the necessary patches to address the integer overflow conditions. System administrators should also implement input validation measures to limit string lengths processed by curl functions, particularly in applications handling external input. Network-level protections such as web application firewalls can help detect and block malicious payloads attempting to exploit this vulnerability. Additionally, organizations should conduct thorough security assessments of their PHP applications to identify all potential usage points of curl_escape and related functions, ensuring comprehensive protection against similar integer overflow vulnerabilities in the broader codebase. The fix implemented in PHP 7.0.10 includes proper bounds checking and integer overflow protection mechanisms that prevent the allocation errors and buffer overflows associated with this specific vulnerability.