CVE-2019-19786 in ATasm
Summary
by MITRE
ATasm 1.06 has a stack-based buffer overflow in the parse_expr() function in setparse.c via a crafted .m65 file.
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Analysis
by VulDB Data Team • 03/12/2024
The vulnerability identified as CVE-2019-19786 represents a critical stack-based buffer overflow flaw within the ATasm 1.06 assembler utility specifically within the parse_expr() function located in the setparse.c source file. This vulnerability manifests when the software processes a specially crafted .m65 file, which serves as an assembly source file format for the Atari 6502 processor architecture. The flaw arises from insufficient bounds checking during the parsing of expression constructs within the assembly file, creating an exploitable condition that can be leveraged by malicious actors.
The technical nature of this vulnerability places it firmly within the category of stack-based buffer overflows as classified by CWE-121, which occurs when a program writes data beyond the bounds of a fixed-length stack buffer. In this case, the parse_expr() function fails to validate the length of input data when processing expressions within the .m65 assembly files, allowing an attacker to craft input that exceeds the allocated buffer space. The overflow can potentially overwrite adjacent stack memory locations including return addresses, function parameters, and local variables, leading to arbitrary code execution or system instability.
The operational impact of this vulnerability extends beyond simple exploitation scenarios to encompass broader security implications for systems running ATasm 1.06. An attacker could potentially leverage this flaw to execute malicious code with the privileges of the user running the assembler, which could lead to complete system compromise if the assembler is used in development environments or automated build processes. The vulnerability affects any system that processes .m65 files through ATasm 1.06, including development workstations, build servers, and automated testing environments where assembly code compilation occurs. The attack vector requires the victim to open or process a maliciously crafted .m65 file, making this a file-based vulnerability that could be delivered through social engineering or automated download mechanisms.
Mitigation strategies for CVE-2019-19786 should prioritize immediate patching of ATasm 1.06 to a version that addresses the buffer overflow condition in parse_expr(). System administrators should implement strict input validation procedures for assembly source files, particularly when these files originate from untrusted sources or are automatically processed within build environments. The implementation of address space layout randomization ASLR and stack canaries can provide additional defense-in-depth measures that would make exploitation more difficult even if the underlying vulnerability persists. Organizations should also consider restricting the execution privileges of the assembler utility and implementing sandboxing techniques to limit potential damage from successful exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation could enable attackers to execute arbitrary commands through compromised assembly processing environments.
The vulnerability demonstrates the importance of proper input validation and memory management practices in development tools, particularly those that process user-provided source code files. Software vendors should implement comprehensive testing procedures including fuzzing and static analysis to identify similar buffer overflow conditions in their codebases. The incident highlights the need for security-conscious development practices where buffer boundaries are carefully validated and appropriate defensive programming techniques are employed to prevent stack-based overflows that could lead to remote code execution in development environments.