CVE-2025-38396: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-38396 is a Linux Security Module (LSM)/SELinux bypass vulnerability in the Linux kernel's secretmem subsystem caused by improper handling of the S_PRIVATE inode flag. The flaw was introduced when alloc_anon_inode() was used without subsequently clearing the S_PRIVATE flag, causing LSM and SELinux security checks to be skipped for secretmem file descriptors. It affects Linux kernel versions 6.0 through 6.1.145, 6.2 through 6.6.96, 6.7 through 6.12.36, 6.13 through 6.15.5, and early 6.16 release candidates (rc1–rc4). The vulnerability was published on July 25, 2025, and carries a CVSS v3.1 base score of 7.8 (High) (Red Hat CVE, Feedly).

The root cause is a security regression in the secretmem subsystem (CWE-284: Improper Access Control) where the S_PRIVATE flag — which causes the VFS layer to skip LSM/SELinux permission checks — was not cleared after calling alloc_anon_inode(). The fix exports anon_inode_make_secure_inode() as the correct API for creating anonymous inodes with a proper security context, replacing the flawed pattern of calling alloc_anon_inode() followed by manual inode_init_security_anon(). This same export also enables KVM's guest_memfd to create anonymous inodes with proper security labeling. The attack vector is local, requiring low privileges and no user interaction, as a local user can open a secretmem file descriptor and interact with it without triggering the expected LSM enforcement (Red Hat CVE, Kernel Patches).

A low-privileged local attacker can bypass LSM and SELinux security policy enforcement for secretmem file descriptors, potentially gaining unauthorized access to sensitive memory regions that should be protected by mandatory access control policies. This could lead to information disclosure of secrets stored in secretmem (e.g., cryptographic keys or sensitive application data), integrity violations, and in the worst case, full compromise of the security context enforced by SELinux or other LSMs. The availability impact is also rated High in the CVSS scoring, suggesting potential for denial-of-service conditions in affected configurations (Red Hat CVE, Feedly).

There is no public proof-of-concept exploit code and no evidence of in-the-wild exploitation as of the time of this report (Feedly). The EPSS score is approximately 0.018% (0.000180), indicating a very low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported. Exploitation requires local access with low privileges, limiting the attack surface primarily to multi-tenant or shared systems where untrusted local users are present.

The Linux kernel project has released patches for all affected stable branches: upgrade to kernel 6.1.146+, 6.6.97+, 6.12.37+, 6.15.6+, or 6.16-rc5+ to remediate the vulnerability (Red Hat CVE, Kernel Patches). Red Hat has issued an advisory (RHSA-2025:16904) and Ubuntu has published USN-7834-1 for affected distributions. SUSE has also released kernel updates (SUSE-2025-03646-1, SUSE-2025-3765-1). As a workaround where patching is not immediately possible, restrict local user access to minimize exposure, and ensure SELinux or other LSMs are properly configured and enforced. Regularly audit system security configurations and monitor for unexpected access to secretmem file descriptors.

Red Hat issued a formal CVE advisory and Bugzilla entry (BZ#2383441) for this vulnerability, and multiple downstream distributions including Ubuntu, SUSE, AlmaLinux, and Oracle Linux have released kernel updates addressing it (Red Hat CVE, Ubuntu USN-7834-1). Security scanner vendors Tenable (Nessus) and Qualys have added detection plugins for this CVE. Coverage has appeared in Linux security news outlets including linuxsecurity.com and pro-linux.de, though no significant social media discussion or notable researcher commentary has been identified beyond routine patch tracking.