CVE-2026-80846
Received Received - Intake

ESP-in-TCP Packet Handling Flaw in Linux Kernel

Publication date: 2026-09-04

Last updated on: 2026-09-04

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: xfrm: drop ESP-in-TCP packets with no ingress device ESP-in-TCP receives records through the TCP strparser. handle_esp() restores skb->dev from the saved skb_iif before passing the packet into the XFRM input path. Queued TCP data can be processed after the original ingress device has been removed, for example during veth or net namespace teardown. In that case dev_get_by_index_rcu() returns NULL. The XFRM IPv4 and IPv6 input paths both expect skb->dev to be valid while building the route lookup, so queued ESP-in-TCP data can dereference a NULL device. Drop the packet if the saved ingress device can no longer be resolved. Such a packet can no longer be routed through the normal XFRM receive path, and this preserves the existing behaviour for packets whose ingress device still exists.

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Meta Information

Published
2026-09-04
Last Modified
2026-09-04
Generated
2026-09-04
AI Q&A
2026-09-04
EPSS Evaluated
N/A
NVD
CVE-2026-80846
EUVD
EUVD-2026-71296

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves ESP-in-TCP packets being processed after the original network device is removed. The kernel attempts to restore the packet's device context but fails if the device no longer exists, leading to a NULL pointer dereference in the XFRM input path for IPv4 and IPv6. The fix drops such packets to prevent crashes.

Detection Guidance

This vulnerability involves ESP-in-TCP packets with no valid ingress device in the Linux kernel. Detection requires monitoring for kernel logs or network traffic anomalies related to XFRM processing. Check kernel logs for NULL pointer dereference errors in XFRM paths using commands like dmesg | grep -i xfrm or journalctl -k | grep -i xfrm.

Impact Analysis

If exploited, this flaw could cause a system crash or denial of service by triggering a kernel panic when maliciously crafted ESP-in-TCP packets are processed after a network device is removed. It primarily affects systems using IPsec with ESP-in-TCP encapsulation.

Mitigation Strategies

Apply the latest Linux kernel security patches to address the issue. If immediate patching is not possible, monitor for affected ESP-in-TCP traffic and ensure proper device teardown procedures to prevent NULL device references during packet processing.

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