In the Linux kernel, the following vulnerability has been resolved: tipc: prevent GCM nonce reuse on peer key changes TIPC can encrypt traffic… (CVE-2026-98805)

The Linux kernel's Transparent Inter-Process Communication (TIPC) protocol encrypts traffic between nodes using AES-GCM with a unique nonce per packet. Previously, the 64-bit counter portion of the nonce was stored per peer and reset when the peer changed its receive key, while the transmit key and salt remained the same. This caused nonce reuse under the same key, breaking confidentiality and exposing the GCM authentication key. An attacker could exploit this to forge packets by altering ciphertexts and generating valid authentication tags. The vulnerability was resolved by switching nonce generation to use the transmit key's atomic sequence counter shared across all encryptions with that key. This counter is not reset on peer key changes, preventing nonce reuse. The nonce format remains unchanged, preserving compatibility, and a pre-existing key revocation mechanism triggers if the counter wraps to zero.

The vulnerability allows an attacker to break confidentiality of encrypted TIPC traffic and trivially forge packets by exploiting nonce reuse and recovering the GCM authentication key. This compromises the integrity and confidentiality of communications between nodes using TIPC encryption under affected kernel versions.

A fix has been implemented in the Linux kernel to prevent nonce reuse by using a shared atomic counter for nonce generation that persists across peer key changes. Users should apply the updated Linux kernel version containing this fix. Since this is a kernel-level vulnerability, upgrading to the patched kernel version is the recommended remediation. No additional mitigations are indicated.