CVE-2023-53998: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-53998 is a race condition vulnerability in the Linux kernel's hwrng: virtio driver affecting the data_avail and actual entropy data fields. The flaw exists because there is no synchronization between the writer (which fills entropy data from the virtio RNG device) and the reader, allowing a race condition when a new entropy request is triggered at the end of a read operation. It affects Linux kernel versions from 2.6.26 up to the fixed stable releases: 4.19.291, 5.4.251, 5.10.188, 5.15.121, 6.1.39, 6.3.13, 6.4.4, and 6.5. The CVE was published on December 24, 2025, and NVD has not yet assigned a CVSS score (Feedly, CVE.org).

The root cause is a missing memory ordering guarantee (CWE-362: Race Condition) in the virtio-rng driver's read path. When the data_avail counter reaches zero, the driver initiates a new entropy request; if the next reader accesses data_avail before the write completes, it may observe stale or inconsistent data due to the absence of any synchronization primitive between the producer and consumer. The fix applies smp_store_release() when writing data_avail and smp_load_acquire() when first reading it in the read path, ensuring proper memory ordering. Additionally, redundant zeroing of data_idx in random_recv_done and data_avail in request_entropy were removed as they were already guaranteed to be zero at those points (Feedly, CVE.org).

Exploitation of this race condition could result in a reader obtaining uninitialized, stale, or incorrect entropy data from the virtio RNG device, potentially degrading the quality of random numbers provided to the kernel or user-space consumers. In virtualized environments (e.g., KVM/QEMU guests using virtio-rng), this could weaken cryptographic operations that depend on high-quality entropy. The vulnerability does not directly enable remote code execution or privilege escalation, but could undermine the integrity of security-sensitive operations relying on the affected entropy source (Feedly).

The Linux kernel stable tree has released patches across multiple stable branches. Users should upgrade to the following fixed versions or later: 4.19.291, 5.4.251, 5.10.188, 5.15.121, 6.1.39, 6.3.13, 6.4.4, or 6.5. Patches are available via the upstream kernel stable repository. As a workaround where patching is not immediately possible, disabling the virtio-rng driver in virtualized guests (if an alternative entropy source is available) can mitigate exposure, though this may impact entropy availability (Feedly, kernel.org patch 6.4.4).

SUSE has issued kernel security advisories referencing CVE-2023-53998 (SUSE-2026-0281-1 and SUSE-2026-20876-1), indicating downstream Linux distributions are actively backporting the fix. Tenable has published Nessus detection plugins (279973, 302405) for this vulnerability. No notable public researcher commentary or social media discussion has been identified beyond standard vulnerability tracking (LinuxSecurity SUSE Advisory, Tenable).