CVE-2025-71155
📋 TL;DR
This CVE addresses a memory corruption vulnerability in the KVM (Kernel-based Virtual Machine) subsystem for s390 architecture in the Linux kernel. Missing checks in the gmap_helper_zap_one_page() function could allow an attacker with guest VM access to corrupt guest memory under specific circumstances. This primarily affects systems running Linux with KVM virtualization on IBM s390/s390x architecture.
💻 Affected Systems
- Linux kernel with KVM s390 support
📦 What is this software?
Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →⚠️ Risk & Real-World Impact
Worst Case
Memory corruption could lead to guest VM crash, denial of service, or potential escalation to host kernel compromise if combined with other vulnerabilities.
Likely Case
Guest VM instability, crashes, or denial of service affecting virtualized workloads on s390 systems.
If Mitigated
Limited impact with proper isolation between VMs and minimal guest privileges.
🎯 Exploit Status
Exploitation requires access to a guest VM and knowledge of specific conditions to trigger the missing checks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check specific kernel versions containing commits 2af2abbcbf8573100288e8f8aea2dab8a2a0ceb7 and 2f393c228cc519ddf19b8c6c05bf15723241aa96
Vendor Advisory: https://git.kernel.org/stable/c/2af2abbcbf8573100288e8f8aea2dab8a2a0ceb7
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. For distributions: Use package manager (yum update kernel, apt upgrade linux-image). 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable KVM on s390
linuxDisable KVM virtualization if not required on s390 systems
modprobe -r kvm
echo 'blacklist kvm' >> /etc/modprobe.d/blacklist.conf
🧯 If You Can't Patch
- Restrict guest VM access to trusted users only
- Implement strict network segmentation for virtualized environments
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if running on s390 with KVM enabled: uname -r && lsmod | grep kvmCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix commits: git log --oneline | grep -E '2af2abbcbf8573100288e8f8aea2dab8a2a0ceb7|2f393c228cc519ddf19b8c6c05bf15723241aa96'📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages
- Guest VM crash logs
- dmesg errors related to KVM or memory corruption
Network Indicators:
- Unusual guest VM behavior or crashes
SIEM Query:
source="kernel" AND ("KVM" OR "s390" OR "gmap_helper") AND ("error" OR "panic" OR "oops")