CVE-2026-45949
Description
A flaw was found in the Linux kernel's hardware random number generator (hwrng) core. A race condition exists where concurrent or rapid calls to the hwrng_unregister() function can lead to a use-after-free vulnerability. This issue allows the system to attempt to access freed memory, potentially causing system instability or, in severe cases, enabling a local attacker to achieve privilege escalation or execute arbitrary code.
Statement
A race in the hwrng core can leave the global hwrng_fill task pointer stale across fast hwrng_register and hwrng_unregister sequences. This can make hwrng_unregister call kthread_stop on the same task twice or on a task_struct that has already been freed, producing a real use after free in a kernel thread lifetime path. For the CVSS the PR:H is used because reliable triggering normally requires privileged hardware RNG device management, module unload, driver unbind, or hotplug control rather than ordinary local user access. The issue is not network reachable and reading from /dev/hwrng alone is not the relevant trigger path. Impact is primarily availability through kernel warning or crash. Limited confidentiality and integrity impact are kept only for the paranoid interpretation because the bug is a real UAF, but the patch does not show controlled reclaim, arbitrary write, or a strong LPE primitive.
Mitigation
Mitigation for this issue is either not available or the currently available options don't 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 | 4.1 | 4.7 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | High | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory
The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.
Confidentiality
Technical Impact: Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.
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