CVE-2025-71155
Published: 23 January 2026
Summary
CVE-2025-71155 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 8.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-16 (Memory Protection) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2025-71155 is a vulnerability in the Linux kernel's KVM implementation for the s390 architecture. The issue resides in the gmap_helper_zap_one_page() function, where missing checks could lead to memory corruption in the guest virtual machine under specific circumstances. This out-of-bounds write flaw, classified as CWE-787, carries a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
A local attacker on the host system with low privileges can exploit this vulnerability. Exploitation requires low attack complexity and no user interaction, enabling high-impact effects on confidentiality, integrity, and availability within the unchanged scope. The result is memory corruption targeting the guest VM.
The referenced kernel commits provide mitigation by adding the missing checks to gmap_helper_zap_one_page(): https://git.kernel.org/stable/c/2af2abbcbf8573100288e8f8aea2dab8a2a0ceb7 and https://git.kernel.org/stable/c/2f393c228cc519ddf19b8c6c05bf15723241aa96. Security practitioners should update to kernels incorporating these fixes.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-4402
Vulnerability details
In the Linux kernel, the following vulnerability has been resolved: KVM: s390: Fix gmap_helper_zap_one_page() again A few checks were missing in gmap_helper_zap_one_page(), which can lead to memory corruption in the guest under specific circumstances. Add the missing checks.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Local out-of-bounds write in KVM host kernel directly enables privilege escalation via memory corruption affecting the guest VM.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Mandates timely identification, reporting, and patching of kernel flaws like the missing checks in gmap_helper_zap_one_page() to eliminate the out-of-bounds write vulnerability.
Implements memory safeguards to protect against unauthorized out-of-bounds writes and memory corruption in the KVM s390 guest virtual machine.
Requires vulnerability scanning of host kernel versions to identify exposure to CVE-2025-71155 and trigger remediation.