CVE-2017-7868 in International Components for Unicode
Summary
by MITRE
International Components for Unicode (ICU) for C/C++ before 2017-02-13 has an out-of-bounds write caused by a heap-based buffer overflow related to the utf8TextAccess function in common/utext.cpp and the utext_moveIndex32* function.
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Analysis
by VulDB Data Team • 08/09/2025
The vulnerability identified as CVE-2017-7868 affects International Components for Unicode (ICU) for C/C++ versions prior to 2017-02-13 and represents a critical heap-based buffer overflow that can lead to arbitrary code execution. This flaw resides within the utf8TextAccess function located in common/utext.cpp and is specifically triggered by the utext_moveIndex32* function, creating a scenario where malicious input can cause memory corruption. The issue stems from inadequate bounds checking during Unicode text processing operations, particularly when handling UTF-8 encoded text sequences that exceed expected buffer boundaries. Such vulnerabilities are particularly dangerous because they can be exploited to overwrite adjacent memory locations, potentially leading to privilege escalation or system compromise.
The technical implementation of this vulnerability involves the improper handling of text indexing operations within ICU's text access mechanisms. When the utext_moveIndex32* functions process Unicode text, they fail to validate the boundaries of heap-allocated buffers, allowing attackers to craft specially formatted UTF-8 input that causes the application to write data beyond the allocated memory region. This out-of-bounds write behavior creates opportunities for attackers to manipulate program execution flow by overwriting critical memory structures such as function pointers, return addresses, or other control data. The vulnerability manifests when applications using ICU libraries process untrusted Unicode input without proper validation, making it particularly prevalent in text processing applications, web browsers, and any software that handles internationalized text.
From an operational perspective, this vulnerability presents significant risks to organizations relying on ICU for Unicode text processing, as it can be exploited through various attack vectors including web applications, file processing systems, and network protocols that handle Unicode content. The exploitability of this flaw is enhanced by the fact that ICU is widely used across multiple software platforms and operating systems, making the attack surface extensive. Security researchers have classified this issue as having high severity due to its potential for remote code execution, with the attack requiring only that an application using the vulnerable ICU library processes malicious Unicode input. The vulnerability's impact is further amplified by the prevalence of Unicode text processing in modern applications, including email clients, web browsers, document processors, and database systems.
Organizations should implement immediate mitigations including updating to ICU version 2017-02-13 or later, which contains the necessary patches to address the buffer overflow conditions. Additionally, defensive programming practices such as input validation, memory bounds checking, and runtime protections should be implemented to reduce the attack surface. The vulnerability aligns with CWE-121, heap-based buffer overflow, and can be mapped to ATT&CK technique T1059.007 for application execution through command and scripting interpreter. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of older ICU versions within the organization's infrastructure, while also implementing proper input sanitization measures for all Unicode text processing operations to prevent similar issues from occurring in other components of the software stack.