CVE-2014-9654 in International Components for Unicode
Summary
by MITRE
The Regular Expressions package in International Components for Unicode (ICU) for C/C++ before 2014-12-03, as used in Google Chrome before 40.0.2214.91, calculates certain values without ensuring that they can be represented in a 24-bit field, which allows remote attackers to cause a denial of service (memory corruption) or possibly have unspecified other impact via a crafted string, a related issue to CVE-2014-7923.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 12/21/2020
The vulnerability identified as CVE-2014-9654 affects the International Components for Unicode (ICU) library implementation in C/C++ environments, specifically targeting the regular expressions package. This flaw existed in ICU versions prior to the December 3, 2014 release and was notably present in Google Chrome versions before 40.0.2214.91, creating a significant security concern for web browsers and applications relying on ICU for international text processing. The vulnerability stems from improper handling of numeric values during regular expression compilation and execution processes, where the system fails to validate that calculated values can be properly represented within a 24-bit field limitation.
The technical flaw manifests when the ICU regular expression engine processes specially crafted input strings that trigger calculations resulting in values exceeding the 24-bit representation capacity. This memory management issue occurs during the internal processing of regular expressions, where the system does not perform adequate bounds checking on intermediate calculations. The lack of proper validation allows attackers to craft malicious strings that, when processed by the ICU library, cause integer overflow conditions or memory corruption scenarios. This type of vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which represents a well-known class of memory corruption vulnerabilities that can lead to unpredictable behavior and potential exploitation.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as the memory corruption can potentially lead to arbitrary code execution depending on the specific execution environment and memory layout. Remote attackers can leverage this weakness by providing malicious input strings to applications using ICU's regular expression functionality, causing the targeted application to crash or behave unpredictably. The vulnerability is particularly concerning in web browser contexts where user input is processed through regular expressions, as demonstrated by its presence in Google Chrome. This issue represents a variant of the broader class of regular expression denial of service vulnerabilities that have plagued many text processing libraries, with CVE-2014-7923 being a related but distinct manifestation of similar weaknesses in the same codebase.
Mitigation strategies for CVE-2014-9654 primarily involve updating to patched versions of the ICU library, specifically those released after December 3, 2014, and ensuring that affected applications such as Google Chrome are upgraded to versions that incorporate these fixes. Organizations should also implement input validation measures to filter potentially malicious regular expression patterns before processing, though this approach provides only partial protection as the vulnerability exists within the core library implementation. The ATT&CK framework categorizes this vulnerability under the T1059.007 technique for "Command and Scripting Interpreter: Unix Shell" when considering the broader attack surface, though the specific exploitation pathway involves memory corruption rather than direct command execution. Security teams should monitor for any potential exploitation attempts in their networks and ensure that all systems utilizing ICU components are properly patched and updated according to vendor advisories.