CVE-2025-21851
Description
From CVE.org
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix softlockup in arena_map_free on 64k page kernel On an aarch64 kernel with CONFIG_PAGE_SIZE_64KB=y, arena_htab tests cause a segmentation fault and soft lockup. The same failure is not observed with 4k pages on aarch64. It turns out arena_map_free() is calling apply_to_existing_page_range() with the address returned by bpf_arena_get_kern_vm_start(). If this address is not page-aligned the code ends up calling apply_to_pte_range() with that unaligned address causing soft lockup. Fix it by round up GUARD_SZ to PAGE_SIZE << 1 so that the division by 2 in bpf_arena_get_kern_vm_start() returns a page-aligned value.
Statement
The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl. This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space.
For the Red Hat Enterprise Linux 9 to confirm the current state, inspect the sysctl with the command:
cat /proc/sys/kernel/unprivileged_bpf_disabled
The setting of 1 would mean that unprivileged users can not use eBPF, mitigating the flaw.
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 2.3 | 3.3 | 7.8 |
| Attack Vector | Local | Local | Local |
| Attack Complexity | Low | Low | Low |
| Privileges Required | High | Low | Low |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | High |
| Integrity Impact | None | None | High |
| Availability Impact | Low | Low | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU)
Inconsistent locking discipline can lead to deadlock.
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