CVE-2026-68119

/// Technical description

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

tcp: initialize standalone TCP-AO response padding

tcp_v4_send_ack() and tcp_v6_send_response() construct standalone TCP

responses with TCP-AO options. The option length carries the actual MAC

length, but the TCP header length includes the option rounded up to a

four-byte boundary.

tcp_ao_hash_hdr() writes the MAC only. Thus, when the MAC length is not

four-byte aligned, the one to three bytes after the MAC are left

uninitialized and may be transmitted. For the normal TCP-AO hashing

mode, those bytes also have to be initialized before computing the MAC.

Initialize only the alignment padding in the TCP-AO branches, before

hashing the header. Use TCPOPT_NOP, as in the normal TCP-AO output path.

This avoids adding work to non-AO TCP responses while preserving a valid

authenticated header.

/// 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