CVE-2024-26677

What it actually does

Delayed ACK construction in the RXRPC protocol incorrectly sets a reference serial number on packets that cannot serve as valid RTT references, leading to improper protocol state handling in the Linux kernel network stack.

Why it matters to the business

Systems running affected Linux kernels may experience subtle network protocol errors or performance degradation in RXRPC-based communications; organizations must apply kernel updates promptly to avoid operational instability despite low exploitation likelihood.

How an attack unfolds

An attacker would craft RXRPC traffic to trigger delayed ACK generation and attempt to leverage the erroneous serial number for timing or state manipulation, though no public exploits or threat actor campaigns are known.

How to fix it

Upgrade the Linux kernel to a version containing commit 200cb50b9e154434470c8969d32474d38475acc2 or later stable releases that include the fix for delayed ACK serial number handling.

How to confirm the fix worked

Verify the running kernel source includes commit 200cb50b9e154434470c8969d32474d38475acc2; test RXRPC delayed ACK behavior under load to confirm absence of erroneous reference serial numbers.

Typical attack path

1. Identify systems running vulnerable Linux kernel versions with RXRPC enabled
2. Establish or intercept RXRPC protocol sessions
3. Force conditions that generate delayed ACK packets
4. Attempt to use the incorrectly set reference serial for protocol abuse

How to detect it

Review kernel logs and network traces for RXRPC packet anomalies involving serial numbers on delayed ACKs; examine git history or package versions to confirm pre-fix kernels.

What your security team should do

• Prioritize kernel updates on all production systems using RXRPC or AFS-related networking
• Monitor for new stable kernel releases and schedule phased rollouts
• Review network configurations to minimize unnecessary RXRPC exposure until patched