CVE-2026-40553 in gawk
Summary
by MITRE • 07/13/2026
Buffer overflow vulnerability has been found in "extension/readdir.c" program file of gawk (ftype() routine). This issue could be used to crash the program and potentially to achieve code execution, although the latter has not been confirmed to be feasible. It affects gawk in versions 5.4.0 and below.
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Analysis
by VulDB Data Team • 07/13/2026
A critical buffer overflow vulnerability has been identified within the gawk utility's extension module, specifically in the readdir.c file at the ftype() routine. This vulnerability represents a classic memory corruption flaw that occurs when the program attempts to write data beyond the allocated buffer boundaries. The issue manifests in gawk versions 5.4.0 and earlier, where the ftype() function fails to properly validate input lengths before copying data into fixed-size buffers, creating an exploitable condition that could lead to arbitrary code execution or denial of service attacks.
The technical implementation of this vulnerability stems from insufficient bounds checking within the file type determination routine. When gawk processes directory entries through its extension interface, the ftype() function receives file path information without adequate validation of string lengths. This allows malicious input to overflow the predetermined buffer space, potentially overwriting adjacent memory locations including return addresses and program state variables. The vulnerability aligns with CWE-121, which categorizes buffer overflow conditions where insufficient boundary checks permit data to be written beyond allocated memory regions.
The operational impact of this vulnerability extends beyond simple program crashes, as it presents a potential pathway for remote code execution attacks. While the exploitability for full code execution has not been definitively confirmed, the nature of buffer overflows within core utility functions provides attackers with opportunities to manipulate program flow through stack smashing or heap corruption techniques. The gawk utility's widespread use in automated systems and scripting environments increases the potential attack surface significantly, as compromised systems could be leveraged for further lateral movement or persistence establishment.
Organizations utilizing gawk in production environments should implement immediate mitigations including updating to version 5.4.1 or later where the vulnerability has been patched. System administrators should also consider implementing input validation controls at the application level and monitoring for anomalous directory traversal patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management practices in scripting utilities and aligns with ATT&CK technique T1059.006, which covers execution through command and scripting interpreters. Additional defensive measures include deploying runtime protections such as stack canaries and address space layout randomization to reduce exploit reliability, while maintaining comprehensive monitoring of system calls related to file operations and process memory manipulation.