Local File Modification Vulnerability in FreeBSD's KTLS Implementation

CVE-2026-45257

What is CVE-2026-45257?

A vulnerability exists in the KTLS implementation of FreeBSD that allows an unprivileged local user to overwrite the contents of a file. When data is transmitted over a loopback connection and the KTLS receive path is enabled, the received data can directly modify the page cache of file-backed memory. This occurs when the assumption that the mbufs holding received data are anonymous proves false. As a result, an attacker can escalate privileges by altering the contents of setuid binaries or other critical files, leading to potential system control. This vulnerability highlights the risks associated with improper handling of data in network communications.

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