CVE-2016-8618 in macOS
Summary
by MITRE
The libcurl API function called `curl_maprintf()` before version 7.51.0 can be tricked into doing a double-free due to an unsafe `size_t` multiplication, on systems using 32 bit `size_t` variables.
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Analysis
by VulDB Data Team • 10/07/2022
The vulnerability identified as CVE-2016-8618 resides within the libcurl library's curl_maprintf() function, which is part of the widely-used Internet communication library that enables applications to transfer data using various protocols. This flaw represents a classic memory safety issue that can be exploited to cause arbitrary code execution or denial of service conditions. The vulnerability specifically affects versions of libcurl prior to 7.51.0, making it a significant concern for systems that have not been properly updated. The root cause lies in how the function handles memory allocation calculations, particularly when dealing with 32-bit size_t variables that are prevalent in many computing environments.
The technical flaw manifests through an unsafe size_t multiplication operation within the curl_maprintf() implementation. When processing formatted string arguments, the function calculates memory requirements based on input parameters, but fails to properly validate or check for integer overflow conditions during the multiplication process. This unsafe operation can lead to a scenario where a maliciously crafted input causes the function to allocate insufficient memory, followed by a subsequent deallocation that results in a double-free condition. The double-free vulnerability occurs because the flawed memory management logic allows the same memory block to be freed twice, which creates a state where an attacker can potentially manipulate the heap layout and execute arbitrary code.
The operational impact of this vulnerability extends across numerous applications and systems that rely on libcurl for network communications, including web browsers, email clients, and server applications. Attackers can exploit this weakness by crafting specially formatted input strings that trigger the vulnerable code path, potentially leading to remote code execution or system compromise. The vulnerability is particularly dangerous because it can be triggered through any application that utilizes the curl_maprintf() function, making it a widespread concern across the software ecosystem. Systems using 32-bit size_t variables are especially vulnerable since the arithmetic overflow conditions that lead to the double-free are more readily achievable in this environment, as detailed in the CWE-129 vulnerability classification.
The exploitation of this vulnerability aligns with several tactics described in the ATT&CK framework, particularly those related to memory corruption and privilege escalation. The double-free condition can be leveraged as part of a broader attack chain to achieve code execution, making it a valuable target for advanced persistent threats. Organizations should prioritize updating their libcurl installations to version 7.51.0 or later, where the memory allocation calculations have been properly hardened against integer overflow conditions. Additionally, implementing proper input validation and sanitization measures within applications that use libcurl can provide additional defense-in-depth layers. Security researchers have noted that this vulnerability demonstrates the critical importance of proper integer overflow checking in memory management functions, as highlighted in the CWE-191 category for integer underflow and overflow conditions. The vulnerability serves as a reminder of how seemingly minor issues in core library functions can have far-reaching consequences across the entire software ecosystem, emphasizing the need for rigorous security testing and code review processes.