CVE-2016-8617 in macOS
Summary
by MITRE
The base64 encode function in curl before version 7.51.0 is prone to a buffer being under allocated in 32bit systems if it receives at least 1Gb as input via `CURLOPT_USERNAME`.
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Analysis
by VulDB Data Team • 10/07/2022
The vulnerability identified as CVE-2016-8617 affects the curl library version 7.51.0 and earlier, specifically targeting the base64 encoding functionality used when processing authentication credentials through the CURLOPT_USERNAME option. This issue manifests as a buffer under-allocation problem that occurs exclusively on 32-bit systems, creating a potential security risk that could be exploited by malicious actors. The flaw stems from improper memory management within the base64 encoding routine, where the allocated buffer size calculation fails to account for the specific constraints and limitations inherent to 32-bit architectures.
The technical implementation of this vulnerability involves the base64 encode function in curl's internal codebase, where the memory allocation for the encoded output buffer is computed using a formula that does not properly handle large input values. When curl processes authentication data through CURLOPT_USERNAME with inputs exceeding 1 gigabyte in size, the calculation used to determine buffer size becomes inadequate, resulting in insufficient memory allocation. This under-allocation creates a situation where subsequent write operations to the buffer can overwrite adjacent memory regions, potentially leading to memory corruption and unpredictable behavior.
The operational impact of this vulnerability extends beyond simple memory corruption, as it creates opportunities for attackers to exploit the buffer under-allocation for more sophisticated attacks. On 32-bit systems, where memory addressing limitations are more pronounced, the vulnerability becomes particularly dangerous because the memory layout and addressing constraints amplify the potential for successful exploitation. The vulnerability affects any application that relies on curl for HTTP authentication, including web browsers, network monitoring tools, and various network utilities that utilize curl's authentication mechanisms. This makes the attack surface particularly broad, as curl is widely integrated into numerous software applications and systems.
This vulnerability aligns with CWE-122, which addresses improper restriction of operations within a limited memory buffer, and represents a classic example of memory safety issues that can lead to arbitrary code execution. The ATT&CK framework categorizes this under the technique of memory corruption vulnerabilities, specifically targeting the execution of malicious code through buffer overflow conditions. The issue demonstrates how seemingly simple library functions can contain critical flaws when operating under specific architectural constraints, highlighting the importance of thorough testing across different system architectures. The vulnerability underscores the necessity of robust input validation and proper memory management practices in network libraries, particularly those handling authentication credentials that may be subject to malicious manipulation.
Mitigation strategies for CVE-2016-8617 primarily focus on upgrading to curl version 7.51.0 or later, where the buffer allocation logic has been corrected to properly handle large input values on 32-bit systems. Organizations should conduct comprehensive inventory assessments to identify all systems and applications utilizing vulnerable versions of curl, particularly those operating on 32-bit architectures. Additionally, implementing runtime protections such as address space layout randomization and stack canaries can provide additional defense-in-depth measures against potential exploitation attempts. Network administrators should also monitor for unusual authentication patterns that might indicate exploitation attempts, while developers should ensure proper input validation and buffer size calculations in their own code that interfaces with curl or similar libraries. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date security libraries and conducting regular security assessments to identify and remediate potential memory safety issues.