CVE-2026-80871 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
crypto: xilinx-trng - Remove crypto_rng interface
Implementing the crypto_rng interface has no purpose, as it isn't used in practice. It's being removed from other drivers too. Just remove it. This leaves hwrng, which is actually used.
Tagging with 'Cc stable' due to the bugs that this removes:
- xtrng_trng_generate() sometimes returned success even when it didn't fill in all the bytes.
- It was possible for xtrng_trng_generate() and xtrng_hwrng_trng_read() to run concurrently and interfere with each other, as the locking code in xtrng_hwrng_trng_read() was broken.
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Analysis
by VulDB Data Team • 09/04/2026
The Linux kernel driver for Xilinx True Random Number Generators contained a structural flaw related to the implementation of cryptographic interfaces that served no practical purpose while introducing significant stability risks. The specific issue involved the unnecessary inclusion and maintenance of the crypto_rng interface within the xilinx-trng driver. This interface was not utilized in actual operational scenarios, creating dead code that added complexity without providing functional value. In alignment with broader kernel efforts to streamline random number generation drivers by removing unused cryptographic abstractions, this implementation detail has been removed. The removal leaves only the hwrng (hardware random number generator) interface, which is the standard and actively used mechanism for accessing hardware entropy sources in Linux systems.
Beyond code cleanup, addressing this vulnerability resolves two critical functional bugs inherent to the previous crypto_rng implementation. First, the function xtrng_trng_generate exhibited a logic error where it would occasionally return a success status even when it failed to fill all requested bytes with random data. This partial generation of entropy can lead to security vulnerabilities in applications relying on complete randomness for key generation or nonce creation, as they may proceed with insufficiently randomized values under the false assumption that full entropy was provided. Second, there was a concurrency issue where xtrng_trng_generate and xtrng_hwrng_trng_read could execute simultaneously without proper synchronization. The locking mechanism within xtrng_hwrng_trng_read was defective, allowing these operations to interfere with each other. This race condition can result in corrupted state, unpredictable behavior, or potential denial of service conditions for processes attempting to access the random number generator.
From a security classification perspective, this vulnerability aligns with CWE-829, which covers Inclusion of Functionality from Untrusted Control Sources, although more accurately it reflects CWE-401 on Missing Release of Memory after Successful Allocation or similar resource management flaws if viewed through the lens of improper state handling. More pertinently, the concurrency issue relates to CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition'). The failure to properly synchronize access to shared hardware resources allows for race conditions that compromise data integrity and system stability. In terms of attack vectors, while this is primarily a reliability and correctness issue rather than an exploitable remote vulnerability, the partial entropy generation could theoretically be leveraged in scenarios where predictable random numbers weaken cryptographic protocols, relating to weaknesses identified in ATT&CK techniques involving resource manipulation or exploitation of software flaws for denial of service.
The mitigation involves applying the kernel patch that removes the crypto_rng interface entirely from the xilinx-trng driver. This change ensures that only the robust and well-tested hwrng interface is exposed to user space, eliminating the buggy code paths associated with the unused crypto_rng functions. System administrators should ensure their systems are updated with a Linux kernel version containing this fix to prevent potential instability or entropy quality issues on Xilinx-based hardware platforms. Tagging this change as stable ensures that it is backported to long-term support kernels, providing immediate protection for deployed environments against these specific concurrency and data integrity flaws.