CVE-2026-46306

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

flow_dissector: do not dissect PPPoE PFC frames

RFC 2516 Section 7 states that Protocol Field Compression (PFC) is NOT

RECOMMENDED for PPPoE. In practice, pppd does not support negotiating

PFC for PPPoE sessions, and the flow dissector driver has assumed an

uncompressed frame until the blamed commit.

During the review process of that commit [1], support for PFC is

suggested. However, having a compressed (1-byte) protocol field means

the subsequent PPP payload is shifted by one byte, causing 4-byte

misalignment for the network header and an unaligned access exception

on some architectures.

The exception can be reproduced by sending a PPPoE PFC frame to an

ethernet interface of a MIPS board, with RPS enabled, even if no PPPoE

session is active on that interface:

$ 0 : 00000000 80c40000 00000000 85144817

$ 4 : 00000008 00000100 80a75758 81dc9bb8

$ 8 : 00000010 8087ae2c 0000003d 00000000

$12 : 000000e0 0000003

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References