CVE-2023-53998 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
hwrng: virtio - Fix race on data_avail and actual data
The virtio rng device kicks off a new entropy request whenever the data available reaches zero. When a new request occurs at the end of a read operation, that is, when the result of that request is only needed by the next reader, then there is a race between the writing of the new data and the next reader.
This is because there is no synchronisation whatsoever between the writer and the reader.
Fix this by writing data_avail with smp_store_release and reading it with smp_load_acquire when we first enter read. The subsequent reads are safe because they're either protected by the first load acquire, or by the completion mechanism.
Also remove the redundant zeroing of data_idx in random_recv_done (data_idx must already be zero at this point) and data_avail in request_entropy (ditto).
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Analysis
by VulDB Data Team • 02/25/2026
The vulnerability identified as CVE-2023-53998 affects the Linux kernel's virtio random number generator implementation, specifically addressing a race condition that can lead to data corruption and potential security implications. This flaw exists within the hardware random number generator subsystem where the virtio rng device manages entropy data for cryptographic operations. The issue stems from insufficient synchronization mechanisms between the entropy generation process and the data consumption by readers, creating a scenario where concurrent access can result in inconsistent data states.
The technical root cause lies in the improper handling of memory access synchronization between the writer thread that generates new entropy data and the reader threads that consume this data. When the data availability counter reaches zero, the system initiates a new entropy request, but there's no coordination between the write operation that populates the new data and the read operation that consumes it. This race condition occurs specifically at the boundary where a new entropy request concludes just as a read operation begins, creating a window where the reader might access partially written data or stale values.
The vulnerability manifests through the lack of proper memory ordering semantics in the virtio rng driver implementation. The fix implements proper smp_store_release and smp_load_acquire operations to ensure memory ordering consistency when accessing the data_avail variable during read operations. This approach follows established memory model principles and addresses the core synchronization issue by ensuring that writes complete before subsequent reads can access the data. The solution leverages the Linux kernel's memory barrier mechanisms to prevent reordering of memory operations that could lead to race conditions.
The operational impact of this vulnerability extends beyond simple data corruption to potentially compromise the security of cryptographic operations that depend on high-quality random number generation. When entropy data becomes inconsistent due to race conditions, it can weaken the randomness quality used by cryptographic algorithms, making systems more susceptible to attacks that exploit predictable random number sequences. This is particularly concerning in security-sensitive applications where the integrity of random number generation is critical for maintaining cryptographic security properties.
The fix addresses this vulnerability by implementing proper memory ordering through the use of release and acquire semantics for the data_avail variable, which prevents the compiler and CPU from reordering memory operations in ways that could cause race conditions. Additionally, the solution removes redundant zeroing operations that were unnecessary and could potentially interfere with the proper operation of the synchronization mechanisms. This approach aligns with established security practices and follows the principles outlined in the Common Weakness Enumeration (CWE) category CWE-362 for race conditions, ensuring that concurrent access to shared resources is properly protected.
Security implications of this vulnerability are significant as it could potentially allow attackers to predict or manipulate entropy generation patterns, undermining the security of cryptographic protocols that rely on the virtio rng device. The fix ensures that entropy data remains consistent and reliable during concurrent access scenarios, maintaining the integrity of random number generation that is fundamental to secure cryptographic operations. This vulnerability resolution contributes to the overall security posture by preventing potential exploitation that could result in weakened cryptographic security or predictable random number generation. The mitigation strategy follows the ATT&CK framework's approach to addressing system-level vulnerabilities through proper memory synchronization and access control mechanisms, ensuring that security controls are properly implemented at the kernel level where they can have maximum impact on system security.