CVE-2026-98805 Linux CVE debrief

Who should care

Linux kernel developers and maintainers, network administrators, and security teams responsible for Linux kernel-based systems. They should review and apply patches, monitor network traffic, and ensure that the Linux kernel is updated to a version that includes the fix.

Why it matters

The Linux kernel's TIPC protocol vulnerability can lead to GCM nonce reuse on peer key changes, compromising confidentiality and authenticity of encrypted traffic.

• Nonce reuse can compromise the confidentiality and authenticity of encrypted traffic between nodes.
• An attacker can exploit CTR malleability to alter captured ciphertexts and use the recovered authentication key to compute a valid tag for the modified ciphertext.
• The vulnerability requires verification of the Linux kernel version and potential patching to prevent exploitation.

Technical summary

The Linux kernel's TIPC protocol uses a 32-bit prefix (a per-key salt XOR the peer's address) followed by a 64-bit counter as the AES-GCM nonce for packets sent to a known peer. When a peer reports a change in its receive key, TIPC resets the counter, but the sender may still use the same TX key and salt, leading to nonce reuse. This nonce reuse breaks confidentiality and exposes GCM's authentication key. The vulnerability requires verification of the Linux kernel version and potential patching to prevent exploitation. The fix involves using the TX key's existing aead->seqno counter instead of resetting the counter on peer key changes.

Defensive priority

Medium

Recommended defensive actions

• Review and apply the patches provided by the Linux kernel maintainers to fix the vulnerability.
• Ensure that the Linux kernel is updated to a version that includes the fix.
• Monitor network traffic for potential exploitation attempts.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The vulnerability is caused by TIPC's use of a 32-bit prefix (a per-key salt XOR the peer's address) followed by a 64-bit counter as the AES-GCM nonce for packets sent to a known peer. When a peer reports a change in its receive key, TIPC resets the counter, but the sender may still use the same TX key and salt, leading to nonce reuse.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.