Linux Kernel Shared Fragment Handler Vulnerability in Networking Stack

CVE-2026-43503

What is CVE-2026-43503?

A vulnerability has been identified in the Linux kernel's handling of shared fragment markers within the networking stack. Specifically, two functions responsible for fragment transfers fail to correctly propagate fragment flags when moving data between source and destination sockets. This oversight can lead to a state where a socket buffer incorrectly indicates the absence of shared fragments, which can result in unprivileged users being able to write to read-only files through unauthorized access. Proper fixes require ensuring that shared fragment flags are maintained during fragment transfers, preventing potential security risk in networking applications that rely on correct fragment handling.

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