CVE-2025-68313
Description
A flaw was found in the Linux kernel. A local user could exploit a vulnerability in the RDSEED (Random Seed) instruction on AMD Zen5 processors. This issue causes the RDSEED instruction to return a random value of zero, which is inconsistent with expected randomness and incorrectly signals success. This can lead to a denial of service (DoS) by compromising operations that rely on high-quality random number generation.
Statement
A moderate-impact flaw was found in the Linux kernel's use of the RDSEED instruction on AMD Zen5 processors. On affected AMD Zen5 CPUs, the 16-bit and 32-bit register output variants of RDSEED can return a random value of 0 at a rate inconsistent with randomness while incorrectly signaling success (CF=1). A local user on an affected system could exploit this behavior to compromise operations that rely on high-quality random number generation, resulting in a denial of service. Red Hat rates this flaw Moderate, with CVSS 3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (5.5), because the impact on Red Hat products is limited to availability. This differs from the upstream CVE.org record, which scores the issue 7.1 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N) based on potential confidentiality and integrity impact from the consumption of insufficiently random values.
The kernel and kernel-rt packages in Red Hat Enterprise Linux 7, 8, 9, and 10, and the kernel package in Red Hat In-Vehicle OS 1.1, are affected, with fixes currently deferred for these streams; until a fix is delivered, systems running on AMD Zen5 hardware remain exposed to RDSEED returning zero values while signaling success, which can affect the availability of services that depend on that randomness. Red Hat Enterprise Linux 6 is not affected because the vulnerable code is not present. The upstream Linux fix adds a check of the AMD microcode revision to address the inconsistent RDSEED behavior.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | N/A | 7.1 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | High | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
If a PRNG is used for authentication and authorization, such as a session ID or a seed for generating a cryptographic key, then an attacker may be able to easily guess the ID or cryptographic key and gain access to restricted functionality.
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