CVE-2018-16842 in cURL
Summary
by MITRE
Curl versions 7.14.1 through 7.61.1 are vulnerable to a heap-based buffer over-read in the tool_msgs.c:voutf() function that may result in information exposure and denial of service.
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Analysis
by VulDB Data Team • 06/04/2023
The vulnerability identified as CVE-2018-16842 represents a critical heap-based buffer over-read flaw within the curl command-line tool that affects versions from 7.14.1 through 7.61.1. This issue resides in the tool_msgs.c source file within the voutf() function, which serves as a formatting output routine for various informational messages and error reports generated by the curl utility. The flaw manifests when curl processes certain input parameters or command-line arguments that trigger the specific output formatting path, creating a scenario where memory beyond the allocated buffer boundaries is accessed and read. This vulnerability falls under the Common Weakness Enumeration category CWE-125, which specifically addresses out-of-bounds read conditions that can lead to information disclosure and system instability.
The technical implementation of this vulnerability involves the manipulation of curl's message formatting system through carefully crafted inputs that cause the voutf() function to exceed the bounds of its allocated heap memory buffer. When curl processes commands that generate formatted output messages, particularly those involving variable arguments or specific string formatting patterns, the function fails to properly validate the length of the output data against the allocated buffer size. This over-read condition allows attackers to potentially access adjacent memory locations containing sensitive information such as stack contents, heap data, or other process memory segments that may include authentication tokens, cryptographic keys, or other confidential data. The vulnerability can be exploited through various attack vectors including command-line argument manipulation, HTTP request parameters, or file input processing that triggers curl's internal message generation routines.
The operational impact of CVE-2018-16842 extends beyond simple information exposure to encompass potential denial of service conditions that can severely disrupt system operations. When the over-read occurs, the affected curl process may exhibit unpredictable behavior including crashes, memory corruption, or system instability that can result in complete service interruption. In environments where curl is extensively used for automated processes, web scraping, or system administration tasks, this vulnerability can create cascading failures that affect multiple applications depending on curl's functionality. The information exposure aspect poses significant risks to systems where curl is used in security-sensitive contexts, as attackers could potentially extract sensitive data from memory locations that contain authentication credentials, session tokens, or other confidential information. The vulnerability is particularly concerning because curl is a widely deployed utility across multiple operating systems and platforms, making the potential attack surface extensive.
Mitigation strategies for this vulnerability should focus on immediate version upgrades to curl 7.61.2 or later, which contain the necessary patches to address the heap-based buffer over-read condition in the voutf() function. Organizations should implement comprehensive patch management procedures to ensure all affected systems receive updates promptly, particularly in environments where curl is used for critical operations or security-sensitive tasks. Additional defensive measures include implementing proper input validation and sanitization for any curl command invocations, restricting curl execution privileges where possible, and monitoring for unusual curl process behavior that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management practices and input validation in security-critical applications, aligning with ATT&CK technique T1059.007 for command and scripting interpreter usage that could be leveraged to exploit such memory corruption vulnerabilities. System administrators should also consider implementing network-based monitoring to detect potential exploitation attempts through crafted command-line arguments or HTTP request parameters that might trigger the vulnerable code path.