You're not seeing things: Microsoft has issued a warning that a vulnerability with a CVSS score of 7.8 has been found in the Linux kernel. The vulnerability in question is tagged CVE-2026-31431 and, according to the Cybersecurity and Infrastructure Security Agency (CISA), "This Linux Kernel Incorrect Resource Transfer Between Spheres Vulnerability is a frequent attack vector for malicious cyber actors and poses significant risks to the federal enterprise."

The distributions affected are Ubuntu, Red Hat, SUSE, Debian, Fedora, Arch Linux, and Amazon Linux. This could also affect any distribution based on those in the list, which means pretty much every Linux distro that isn't independent.

On this issue, Red Hat has said, "This local privilege escalation is rated as Important severity. Part of the Linux kernel's cryptographic interface contains an incorrect in-place operation, where source and destination data mappings differ. This could lead to data integrity issues, including the escalation to root privileges."

The flaw is found in the Linux kernel cryptographic subsystem's algif_aead module of AF_ALG. The problem is that a particular optimization has led to the kernel reusing the source memory as the destination during cryptographic operations. What this means is that attackers can take advantage of interactions between the AF_ALG socket interface and a splice() system call.

Currently, active exploitation of the vulnerability is limited to proof-of-concept (PoC) demonstrations. Until patches are released, Microsoft is advising that the affected crypto feature should be disabled, or AF_ALG socket creation should be blocked.