CVE-2025-38396
📋 TL;DR
This CVE describes a Linux kernel vulnerability where the S_PRIVATE flag wasn't properly cleared after alloc_anon_inode(), allowing LSM/SELinux security checks to be bypassed for secretmem file descriptors. This affects Linux systems using secretmem or KVM guest_memfd functionality. The vulnerability could allow unauthorized access to protected memory regions.
💻 Affected Systems
- Linux kernel
📦 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 →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 →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 →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
An attacker could bypass LSM/SELinux security policies to access protected secretmem regions, potentially exposing sensitive data or gaining unauthorized access to memory.
Likely Case
Local privilege escalation or unauthorized access to secretmem file descriptors, compromising data confidentiality of protected memory regions.
If Mitigated
With proper LSM/SELinux policies and kernel hardening, impact is limited to specific memory regions rather than full system compromise.
🎯 Exploit Status
Exploitation requires local access and understanding of kernel memory management. No public exploit code is mentioned in the CVE description.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits: 66d29d757c968d2bee9124816da5d718eb352959, 6ca45ea48530332a4ba09595767bd26d3232743b, cbe4134ea4bc493239786220bd69cb8a13493190, e3eed01347721cd7a8819568161c91d538fbf229, f94c422157f3e43dd31990567b3e5d54b3e5b32b
Vendor Advisory: https://git.kernel.org/stable/c/66d29d757c968d2bee9124816da5d718eb352959
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version. 2. Check with your distribution vendor for specific kernel packages. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Disable secretmem functionality
linuxDisable secretmem if not required, reducing attack surface
echo 'kernel.secretmem_enable=0' >> /etc/sysctl.conf
sysctl -p
Restrict KVM access
linuxLimit KVM access to trusted users only
chmod 600 /dev/kvm
setfacl -m u:trusteduser:rw /dev/kvm
🧯 If You Can't Patch
- Implement strict LSM/SELinux policies to limit damage if exploited
- Monitor system logs for unusual secretmem or KVM access patterns
🔍 How to Verify
Check if Vulnerable:
Check kernel version and verify if secretmem/KVM guest_memfd functionality is enabled. Use: cat /proc/version and check for secretmem in kernel config.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits or is newer than patched version. Check with: uname -r and compare with patched versions.📡 Detection & Monitoring
Log Indicators:
- Unusual secretmem file descriptor creation
- Failed LSM/SELinux denials for memory operations
- Unexpected KVM guest_memfd operations
Network Indicators:
- None - this is a local vulnerability
SIEM Query:
Search for kernel audit logs containing 'secretmem' or 'anon_inode' with security context failures🔗 References
- https://git.kernel.org/stable/c/66d29d757c968d2bee9124816da5d718eb352959
- https://git.kernel.org/stable/c/6ca45ea48530332a4ba09595767bd26d3232743b
- https://git.kernel.org/stable/c/cbe4134ea4bc493239786220bd69cb8a13493190
- https://git.kernel.org/stable/c/e3eed01347721cd7a8819568161c91d538fbf229
- https://git.kernel.org/stable/c/f94c422157f3e43dd31990567b3e5d54b3e5b32b
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
