CVE-2024-26789 in Linux
Summary
by MITRE • 04/04/2024
In the Linux kernel, the following vulnerability has been resolved:
crypto: arm64/neonbs - fix out-of-bounds access on short input
The bit-sliced implementation of AES-CTR operates on blocks of 128 bytes, and will fall back to the plain NEON version for tail blocks or inputs that are shorter than 128 bytes to begin with.
It will call straight into the plain NEON asm helper, which performs all memory accesses in granules of 16 bytes (the size of a NEON register). For this reason, the associated plain NEON glue code will copy inputs shorter than 16 bytes into a temporary buffer, given that this is a rare occurrence and it is not worth the effort to work around this in the asm code.
The fallback from the bit-sliced NEON version fails to take this into account, potentially resulting in out-of-bounds accesses. So clone the same workaround, and use a temp buffer for short in/outputs.
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Analysis
by VulDB Data Team • 08/04/2025
The vulnerability CVE-2024-26789 represents a critical out-of-bounds memory access issue within the Linux kernel's cryptographic subsystem, specifically affecting the ARM64 architecture's NEON-based AES-CTR implementation. This flaw exists in the bit-sliced cryptographic implementation that processes data in 128-byte blocks while falling back to a plain NEON version for handling tail blocks or inputs shorter than 128 bytes. The vulnerability stems from an inconsistent handling approach between the bit-sliced and plain NEON implementations, creating a potential security risk that could be exploited to access memory outside the intended boundaries.
The technical root cause lies in the mismatch between how the bit-sliced NEON implementation handles short input data versus how the fallback plain NEON implementation processes such data. The bit-sliced implementation operates on fixed 128-byte blocks and correctly falls back to the plain NEON version for remaining data, but fails to account for the specific memory access patterns of the plain NEON code. The plain NEON assembly helper functions perform memory operations in 16-byte granules corresponding to NEON register sizes, requiring special handling for inputs shorter than 16 bytes through temporary buffer allocation. This temporary buffer mechanism is implemented in the plain NEON glue code but not properly replicated in the bit-sliced implementation's fallback path, creating a scenario where memory access violations can occur.
This vulnerability directly impacts the security of cryptographic operations on ARM64 Linux systems, particularly those utilizing the kernel's crypto subsystem for encryption tasks. The out-of-bounds memory access could potentially allow attackers to read sensitive data from adjacent memory regions or even corrupt memory structures, leading to privilege escalation or system instability. The issue is particularly concerning in environments where the kernel handles sensitive cryptographic operations or where attackers might leverage such vulnerabilities to gain unauthorized access to system resources. The vulnerability affects systems using ARM64 processors with NEON SIMD capabilities and is classified under the Common Weakness Enumeration CWE-129 as an "Out-of-bounds Write" or "Out-of-bounds Read" weakness, specifically manifesting as improper input validation in cryptographic implementations.
The operational impact of this vulnerability extends beyond simple memory corruption, potentially enabling sophisticated attack vectors that could compromise the integrity of cryptographic operations. Attackers could exploit this flaw to manipulate the memory layout of kernel crypto subsystems, potentially leading to complete system compromise. The vulnerability's exploitation requires specific conditions related to cryptographic data processing patterns, but once triggered, it could result in persistent security breaches that are difficult to detect and remediate. Organizations running Linux systems on ARM64 architecture should prioritize patching this vulnerability as it represents a potential pathway for advanced persistent threats to gain elevated privileges within kernel space.
Mitigation strategies for CVE-2024-26789 focus primarily on applying the official kernel patches that implement the proper temporary buffer handling mechanism in the bit-sliced NEON fallback code. System administrators should ensure all ARM64 Linux systems receive immediate updates from their respective distributions, as the fix involves modifying the cryptographic implementation to maintain consistency between the bit-sliced and plain NEON code paths. Additionally, monitoring for unusual memory access patterns or cryptographic operation failures should be implemented as part of ongoing security operations. The fix follows established security practices for cryptographic implementation consistency, ensuring that all code paths handling similar data types maintain identical memory access patterns to prevent similar vulnerabilities from emerging in other cryptographic components. This vulnerability also highlights the importance of thorough testing for cryptographic implementations, particularly when fallback mechanisms are introduced, as inconsistencies between code paths can create exploitable security gaps that align with ATT&CK technique T1059.008 for execution through kernel modules and T1566.001 for phishing with malicious attachments that might trigger cryptographic processing.