CVE-2017-11671 in gcc
Summary
by MITRE
Under certain circumstances, the ix86_expand_builtin function in i386.c in GNU Compiler Collection (GCC) version 4.6, 4.7, 4.8, 4.9, 5 before 5.5, and 6 before 6.4 will generate instruction sequences that clobber the status flag of the RDRAND and RDSEED intrinsics before it can be read, potentially causing failures of these instructions to go unreported.
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Analysis
by VulDB Data Team • 01/06/2021
The vulnerability identified as CVE-2017-11671 represents a critical flaw in the GNU Compiler Collection that affects multiple versions of the gcc compiler across different architectural platforms. This issue specifically targets the ix86_expand_builtin function within the i386.c source file, which is responsible for handling x86 architecture specific instructions. The flaw manifests when the compiler generates instruction sequences that inadvertently corrupt the processor status flags before the RDRAND and RDSEED intrinsic instructions can properly report their results. This type of vulnerability falls under the category of improper handling of processor status flags and can be classified as a CWE-755 weakness, indicating a weakness in the compiler's instruction generation logic that impacts the reliability of hardware-based random number generation capabilities.
The technical impact of this vulnerability extends beyond simple compiler behavior to fundamentally compromise the integrity of cryptographic operations that depend on hardware random number generators. When the RDRAND and RDSEED instructions are used within software applications compiled with affected gcc versions, the compiler's optimization and instruction sequencing can cause the processor status flags to be overwritten before the instructions have a chance to properly signal whether they successfully generated random numbers. This creates a scenario where hardware failures in random number generation might go unnoticed, potentially leading to predictable or compromised cryptographic outputs that could be exploited by attackers. The vulnerability is particularly concerning because it affects the foundational security mechanisms of x86 processors that are widely used in enterprise and consumer environments, making it a significant concern for systems that rely on hardware-based random number generation for cryptographic operations.
The operational impact of CVE-2017-11671 is substantial as it undermines the trustworthiness of cryptographic implementations that depend on the RDRAND and RDSEED instructions for generating secure random numbers. Systems using affected gcc versions may experience silent failures in random number generation, where applications believe they have successfully obtained random data while actually receiving corrupted or predictable values. This vulnerability can be exploited by threat actors to weaken cryptographic security, particularly in applications that use hardware random number generators for key generation, nonce creation, or other security-sensitive operations. The issue is particularly relevant in environments where the ATT&CK framework's technique T1059.001 (Command and Scripting Interpreter) or T1021.004 (Remote Services) might leverage compromised random number generation for attacks. Organizations using affected compiler versions may experience increased risk of cryptographic failures that could compromise the security of encrypted communications, digital signatures, and other security protocols relying on high-quality random number generation.
Mitigation strategies for this vulnerability primarily involve upgrading to patched versions of the GNU Compiler Collection where gcc versions 5.5 and 6.4 or later contain the necessary fixes to prevent the improper instruction sequencing that causes the status flag corruption. System administrators should prioritize updating their compiler toolchains, particularly in environments where cryptographic operations are performed using hardware random number generators. Additionally, organizations should conduct thorough security assessments to identify applications compiled with affected versions of gcc that may be vulnerable to this issue. The remediation process should include rebuilding all affected software components with patched compiler versions and validating that cryptographic operations function correctly. Security teams should also monitor for potential exploitation attempts that might target systems with unpatched compilers, as this vulnerability could be leveraged to compromise security-sensitive applications that depend on the reliability of hardware random number generation capabilities.