CVE-2026-38753 in Busybox
Summary
by MITRE • 07/15/2026
A use-after-free in the awk_sub() function (editors/awk.c) of Busybox v1.38.0 allows attackers to cause a Denial of Service (DoS) via supplying a crafted AWK script.
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Analysis
by VulDB Data Team • 07/15/2026
The vulnerability under discussion represents a critical use-after-free condition within the awk_sub() function located in the editors/awk.c file of Busybox version 1.38.0. This type of memory safety issue occurs when a program continues to reference memory locations after they have been freed, creating potential for system instability and exploitation. The specific context involves the AWK scripting interpreter functionality within Busybox, which is widely deployed across embedded systems, routers, and IoT devices where resource constraints make such vulnerabilities particularly dangerous.
The technical flaw manifests in how the awk_sub() function handles memory allocation and deallocation during the processing of AWK scripts. When an attacker supplies a crafted script that triggers specific patterns of string substitution operations, the function fails to properly manage the lifecycle of allocated memory blocks. This improper memory management creates a situation where freed memory locations become accessible for subsequent operations, leading to undefined behavior when the system attempts to access or modify this already-released memory region.
The operational impact of this vulnerability extends beyond simple denial of service, as it demonstrates a fundamental flaw in the memory management practices within embedded system toolchains. The DoS condition can be reliably triggered through crafted AWK input, potentially allowing attackers to disrupt services on devices running Busybox v1.38.0, including network appliances, embedded routers, and various IoT implementations. Given that Busybox is commonly used as a core component in many Linux-based embedded systems, this vulnerability affects a broad spectrum of devices where system availability is crucial for operational integrity.
This vulnerability aligns with CWE-416, which specifically addresses the use of freed memory condition, and represents a classic example of improper memory management patterns that have been documented across numerous security advisories. The ATT&CK framework would categorize this as a system service exploitation technique, where an attacker leverages memory corruption vulnerabilities to disrupt normal system operations. Mitigation strategies should focus on implementing proper memory management practices including bounds checking, using safe string manipulation functions, and applying comprehensive input validation for all script processing components. Additionally, organizations should consider upgrading to patched versions of Busybox, implementing runtime protections such as address space layout randomization, and conducting thorough security reviews of embedded system toolchains to identify similar memory safety issues.
The broader implications highlight the importance of rigorous security testing in embedded environments where traditional software security practices may not be fully implemented. This vulnerability serves as a reminder that even seemingly simple utilities within system toolchains can contain critical flaws that affect millions of devices globally, emphasizing the need for comprehensive security practices throughout the software development lifecycle.