CVE-2017-9728 in uClibc
Summary
by MITRE
In uClibc 0.9.33.2, there is an out-of-bounds read in the get_subexp function in misc/regex/regexec.c when processing a crafted regular expression.
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Analysis
by VulDB Data Team • 08/25/2025
The vulnerability identified as CVE-2017-9728 represents a critical out-of-bounds read flaw within the uClibc C library implementation that affects systems utilizing this lightweight C library for embedded environments. This vulnerability specifically resides in the get_subexp function located within the misc/regex/regexec.c file of uClibc version 0.9.33.2, making it particularly concerning for embedded systems and IoT devices that commonly rely on uClibc for their runtime environment. The flaw occurs during the processing of crafted regular expressions, which means that an attacker can potentially trigger this vulnerability through malicious input patterns that are designed to exploit the boundary conditions within the regular expression engine.
The technical implementation of this vulnerability stems from inadequate bounds checking within the regular expression parsing logic of uClibc's implementation. When the get_subexp function processes a specially crafted regular expression, it fails to properly validate array access boundaries, leading to memory reads that extend beyond the allocated buffer space. This out-of-bounds read can result in information disclosure, as the function may access memory locations that contain sensitive data from adjacent memory regions. The vulnerability manifests as a classic buffer overread condition that can be classified under CWE-125 as an out-of-bounds read, which falls within the broader category of memory safety issues that have become increasingly prevalent in modern software systems.
From an operational impact perspective, this vulnerability poses significant risks to embedded systems and network appliances that utilize uClibc for their regular expression processing capabilities. Systems such as routers, firewalls, and network monitoring appliances that process user input through regular expression matching functions are particularly susceptible to exploitation. The vulnerability can potentially be leveraged by attackers to extract sensitive information from memory, including cryptographic keys, passwords, or other confidential data that may be stored in adjacent memory locations. Additionally, the out-of-bounds read could lead to application crashes or denial of service conditions, disrupting critical network services and potentially providing attackers with opportunities for further exploitation.
The attack surface for this vulnerability is particularly wide given that uClibc is commonly used in embedded environments where regular expression processing is prevalent for log parsing, configuration validation, and network traffic filtering. The exploitation of this vulnerability requires an attacker to construct a specific regular expression pattern that triggers the flawed boundary checking logic, making it a targeted rather than broadly exploitable vulnerability. However, the impact remains severe as it can be used to compromise the confidentiality and integrity of data processed by affected systems, aligning with ATT&CK technique T1059.007 for command and scripting interpreter usage in contexts where regular expressions are processed. Organizations should consider this vulnerability as part of their broader security posture assessment, particularly for embedded systems that may be exposed to untrusted input through network interfaces or user interaction points.
Mitigation strategies for CVE-2017-9728 primarily involve upgrading to a patched version of uClibc that addresses the out-of-bounds read condition in the get_subexp function. System administrators should also implement input validation and sanitization measures to prevent malicious regular expressions from reaching the vulnerable code path. Additionally, deploying intrusion detection systems that can identify suspicious regular expression patterns and implementing memory protection mechanisms such as stack canaries or address space layout randomization can provide additional layers of defense against exploitation attempts. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing uClibc and ensure proper patch management procedures are in place to maintain system security.