Cyber Resilience

CVE-2025-21851

Linux Kernel 6.9 – 6.12.17

Published
12 March 2025
Modified
30 July 2026
Patch / advisory
View advisory
CVSS Score v3.1 7.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0017 7th percentile
Risk Priority 55 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2025-21851 is a high-severity Improper Locking (CWE-667) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability Data

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…

more

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.

CWE(s)
CWE-667

Related Threats

MITRE ATT&CK Enterprise Techniques

T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1548 Abuse Elevation Control Mechanism Privilege Escalation
Adversaries may circumvent mechanisms designed to control privilege elevation to gain higher-level permissions.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

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CVE-2024-43862Same product: Linux Linux Kernel
CVE-2025-22012Same product: Linux Linux Kernel
CVE-2024-40912Same product: Linux Linux Kernel
CVE-2025-22077Same product: Linux Linux Kernel
CVE-2024-35968Same product: Linux Linux Kernel
CVE-2026-53049Same product: Linux Linux Kernel

Affected Assets

linux
linux kernel
6.14, 6.9 · 6.9 — 6.12.17 · 6.13 — 6.13.5

Mitigating Controls

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly include code reviews, static analysis, and concurrency standards that prevent improper locking.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect race conditions and locking errors before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle includes concurrency and locking requirements that reduce improper locking defects.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate proper lock acquisition/release patterns.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles address thread-safety and resource synchronization.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prohibit missing or incorrect lock usage.

A.8.32 Change management partial match
prevents

Change management may catch locking issues introduced by modifications but does not prevent the weakness itself.

References