CVE-2019-16277 in PicoC
Summary
by MITRE
PicoC 2.1 has a heap-based buffer overflow in StringStrcpy in cstdlib/string.c when called from ExpressionParseFunctionCall in expression.c.
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Analysis
by VulDB Data Team • 12/25/2023
The vulnerability identified as CVE-2019-16277 represents a critical heap-based buffer overflow within the PicoC 2.1 interpreted programming language implementation. This flaw exists in the string handling subsystem of the software, specifically within the StringStrcpy function located in the cstdlib/string.c file. The vulnerability manifests when this function is invoked through the ExpressionParseFunctionCall routine found in expression.c, creating a chain of function calls that ultimately leads to memory corruption. The issue stems from inadequate bounds checking during string copy operations, allowing malicious input to overwrite adjacent memory regions beyond the allocated buffer boundaries.
This heap-based buffer overflow constitutes a significant security risk as it can be exploited to execute arbitrary code or cause application crashes. The vulnerability falls under CWE-121, which categorizes heap-based buffer overflows as a critical weakness in memory management. When an attacker successfully triggers this vulnerability, they can manipulate the program's execution flow by overwriting critical memory locations including return addresses, function pointers, or other control data structures. The exploitation typically requires careful crafting of input data that specifically targets the string processing functions within PicoC's interpreter, making it a sophisticated attack vector that demands precise control over memory layout.
The operational impact of CVE-2019-16277 extends beyond simple application instability to potentially enable remote code execution in environments where PicoC is used as an embedded scripting engine. Systems that incorporate PicoC for dynamic code execution, configuration scripting, or plugin architectures become vulnerable to attacks that could compromise the entire host environment. The vulnerability affects any application or system utilizing PicoC 2.1 that processes untrusted input through string operations, particularly in contexts where the interpreter handles external data or user-provided scripts. This makes it especially dangerous in web applications, embedded systems, or any environment where PicoC serves as a code execution engine for user-supplied content.
Mitigation strategies for this vulnerability should focus on immediate code-level fixes including implementing proper bounds checking in the StringStrcpy function and ensuring all string operations validate input lengths against allocated buffer sizes. The recommended approach involves upgrading to PicoC versions that have addressed this specific buffer overflow issue, as the original implementation lacks proper memory management safeguards. Additionally, input validation mechanisms should be strengthened to prevent overly long strings from being processed, and runtime protections such as stack canaries, address space layout randomization, and heap protection mechanisms should be enabled to reduce exploitability. Organizations should also implement monitoring and logging of string processing operations to detect potential exploitation attempts, while following ATT&CK framework tactics related to defensive techniques for memory corruption vulnerabilities. The fix should align with secure coding practices outlined in industry standards to prevent similar issues in future implementations of similar string handling functions.