CVE-2017-20229: Invisible-island Mawk Buffer Overflow

CVE-2017-20229 Overview

CVE-2017-20229 is a stack-based buffer overflow vulnerability affecting MAWK (Mike's AWK) version 1.3.3-17 and prior. The vulnerability exists due to inadequate boundary checks on user-supplied input, allowing attackers to craft malicious input that overflows the stack buffer. Successful exploitation enables attackers to execute arbitrary code by leveraging return-oriented programming (ROP) techniques to spawn a shell with application privileges.

Critical Impact

This vulnerability allows remote attackers to achieve arbitrary code execution on affected systems running vulnerable versions of MAWK, potentially leading to complete system compromise.

Affected Products

• Invisible-island MAWK versions up to and including 1.3.3-17
• Systems with MAWK installed as the default AWK implementation
• Applications and scripts that process untrusted input through MAWK

Discovery Timeline

• 2026-03-28 - CVE-2017-20229 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2017-20229

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), a memory corruption flaw where the application writes data past the boundaries of an allocated buffer on the stack. The root cause stems from insufficient validation of input length before copying data into fixed-size stack buffers within MAWK's parsing routines.

When processing AWK programs or input data, MAWK fails to properly validate the size of certain user-controlled input before storing it in stack-allocated buffers. An attacker can supply input that exceeds the expected buffer size, causing a stack buffer overflow condition that corrupts adjacent memory, including saved return addresses and frame pointers.

Root Cause

The vulnerability originates from missing or improper bounds checking during input processing operations in MAWK. The application allocates fixed-size buffers on the stack and copies user-supplied data without verifying that the input length does not exceed the buffer capacity. This classic stack-based buffer overflow condition allows attackers to overwrite critical stack data structures.

Attack Vector

The attack is network-accessible, requiring no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Crafting a malicious AWK program or input data with oversized fields
2. Submitting this input to a system running a vulnerable MAWK version
3. Overflowing the stack buffer to overwrite the saved return address
4. Executing a return-oriented programming (ROP) chain to bypass security controls
5. Spawning a shell with the privileges of the MAWK process

Technical details and proof-of-concept information are available through the Exploit-DB #42357 entry and the VulnCheck Advisory on mawk Buffer Overflow.

Detection Methods for CVE-2017-20229

Indicators of Compromise

• Unexpected MAWK process crashes or abnormal termination signals (SIGSEGV, SIGABRT)
• Unusual child processes spawned by MAWK executables
• Memory access violations in system logs related to MAWK execution
• Suspicious shell activity originating from AWK interpreter processes

Detection Strategies

• Monitor for MAWK process execution with unusually large input files or command-line arguments
• Deploy application-level monitoring to detect stack-smashing protection (SSP) violations
• Implement file integrity monitoring on MAWK binaries and configuration files
• Use SentinelOne's behavioral AI engine to detect exploitation attempts and anomalous process spawning patterns

Monitoring Recommendations

• Enable core dump analysis for MAWK-related crashes to identify exploitation attempts
• Configure SIEM rules to alert on unusual process hierarchies involving MAWK
• Monitor network traffic for large or malformed data being sent to systems running vulnerable MAWK versions
• Deploy SentinelOne Singularity to gain real-time visibility into process behavior and memory manipulation attempts

How to Mitigate CVE-2017-20229

Immediate Actions Required

• Upgrade MAWK to a version newer than 1.3.3-17 that contains the security fix
• Where possible, replace MAWK with alternative AWK implementations (gawk, nawk) that are not affected
• Restrict execution of MAWK with untrusted input using sandboxing or containerization
• Apply operating system-level protections such as ASLR, DEP/NX, and stack canaries

Patch Information

Organizations should update to the latest version of MAWK available from the Invisible-island project. Refer to the VulnCheck Advisory on mawk Buffer Overflow for specific patching guidance and version recommendations.

Workarounds

• Implement input validation and size restrictions before passing data to MAWK
• Run MAWK processes in restricted environments with minimal privileges (principle of least privilege)
• Use security wrappers or containers to isolate MAWK execution from critical system components
• Consider disabling MAWK on systems where it is not required

For systems where immediate patching is not feasible, administrators can implement input sanitization at the application layer to limit the size and format of data processed by MAWK. Additionally, compiling MAWK with stack protection flags (-fstack-protector-strong) and enabling ASLR can increase exploitation difficulty, though these are defense-in-depth measures and not complete mitigations.