CVE-2016-8621 in macOS
Summary
by MITRE
The `curl_getdate` function in curl before version 7.51.0 is vulnerable to an out of bounds read if it receives an input with one digit short.
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Analysis
by VulDB Data Team • 10/07/2022
The CVE-2016-8621 vulnerability affects the curl library's `curl_getdate` function, which is responsible for parsing date strings used in various internet protocols including http and ftp. This function processes date and time information from server responses and header fields, making it a critical component in the network communication stack. The vulnerability manifests when the function receives malformed date input that is exactly one digit short of the expected format, creating a scenario where memory access occurs beyond the allocated buffer boundaries. The issue is particularly concerning because date parsing is fundamental to many network operations including cookie handling, cache management, and authentication token validation.
The technical flaw stems from improper bounds checking within the date parsing algorithm. When the `curl_getdate` function encounters a date string with one digit missing from the expected format, it continues processing without proper validation of input length or structure. This allows the function to read memory locations beyond the intended buffer, potentially accessing uninitialized data or memory belonging to other variables. The out of bounds read can result in information disclosure, application crashes, or in some cases, provide a foothold for more sophisticated attacks depending on the memory layout and surrounding data. This type of vulnerability falls under the CWE-125 Out-of-bounds Read classification, which represents a common weakness where programs read data past the end of valid buffer boundaries.
The operational impact of this vulnerability extends beyond simple application instability. In web applications and network services that rely on curl for HTTP operations, an attacker could potentially craft malicious date responses that trigger this out of bounds read during normal operation. This could lead to denial of service conditions where applications crash or become unresponsive, or worse, allow for information leakage that might reveal sensitive memory contents including cryptographic keys, session tokens, or other confidential data. The vulnerability affects curl versions prior to 7.51.0, making it particularly relevant for systems that have not been updated, and represents a security risk in environments where curl is used extensively for network communication.
Mitigation strategies for CVE-2016-8621 primarily involve updating to curl version 7.51.0 or later, which contains the necessary patches to address the bounds checking issue in the `curl_getdate` function. Organizations should also implement input validation measures at application layers that use curl, ensuring that date strings are properly formatted before being passed to the library functions. Network monitoring and intrusion detection systems should be configured to detect unusual date parsing behavior that might indicate exploitation attempts. Additionally, security teams should consider implementing application sandboxing or memory protection mechanisms to limit the potential impact if such vulnerabilities are exploited in environments where updates cannot be immediately applied. The vulnerability demonstrates the importance of robust input validation and proper memory management in security-critical libraries that handle user-supplied data.