CVE-2026-31468: 
Linux Kernel vulnerability analysis and mitigation

CVE-2026-31468 is a double free vulnerability in the Linux kernel's vfio/pci dma-buf feature, specifically within the vfio_pci_core_feature_dma_buf() function. The flaw was disclosed on April 22, 2026, and affects Linux kernel versions 6.19 through 6.19.11 (exclusive) as well as Linux kernel 7.0 release candidates (rc1 through rc5). The vulnerability carries a CVSS v3.1 base score of 7.8 (High) (GitHub Advisory, Red Hat Bugzilla).

The root cause is improper error handling in the vfio_pci_core_feature_dma_buf() function, classified as CWE-415 (Double Free) and CWE-763 (Release of Invalid Pointer or Reference). When file descriptor exhaustion occurs during dma-buf operations, the error path falls through the entire unwind chain instead of limiting cleanup to only dma_buf_put() after dma_buf_export(), resulting in an unbalanced reference count on the vfio device and a double free of allocated memory objects. Exploitation requires local access with low privileges (e.g., a user with access to a vfio/pci device), and the triggering condition — file descriptor exhaustion — is an unlikely but achievable scenario. The fix moves the put operation directly into the error path and returns the errno, bypassing the problematic unwind chain (GitHub Advisory, Red Hat Bugzilla).

Successful exploitation can lead to kernel memory corruption due to the double free condition, potentially resulting in system instability, denial of service, or — depending on exploit complexity and system configuration — arbitrary code execution in kernel context. Because the vulnerability affects the vfio/pci subsystem used for device passthrough in virtualization environments, exploitation could impact hypervisor stability and potentially affect guest isolation. Confidentiality, integrity, and availability are all rated High in the CVSS assessment (GitHub Advisory).

There is no known public proof-of-concept exploit and no evidence of in-the-wild exploitation at this time. The EPSS score is approximately 0.018% (4th percentile), indicating a low near-term exploitation probability. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Triggering the vulnerability requires inducing file descriptor exhaustion in a system using vfio/pci dma-buf functionality, which limits opportunistic exploitation (GitHub Advisory, Red Hat Bugzilla).

Apply the upstream kernel patches available at the official kernel stable repository commits 83ad334afc9a645cef1062f5346526b1e36d6516 and e98137f0a874ab36d0946de4707aa48cb7137d1c, which fix the double free condition in vfio_pci_core_feature_dma_buf(). Systems running Linux kernel 6.19 should upgrade to 6.19.11 or later; kernel 7.0 users should apply the fix targeting the 7.0 stable branch. As a complementary measure, administrators should implement file descriptor limits (e.g., via ulimit or systemd LimitNOFILE) and monitor for file descriptor exhaustion events on systems using vfio/pci passthrough (GitHub Advisory, Red Hat Bugzilla).