CVE-2026-80976 Linux CVE debrief

Who should care

Linux kernel maintainers and users, network administrators, security teams responsible for Linux systems, and operators of systems using the Linux kernel should verify and apply patches, monitor network traffic, and update systems to prevent potential denial of service.

Why it matters

A vulnerability in the Linux kernel's seg6 implementation can cause an out-of-bounds read when processing IPv6 packets. Linux kernel maintainers and users, network administrators, and security teams should verify and apply patches, monitor network traffic, and update systems to prevent potential denial of service.

• Potential denial of service due to out-of-bounds read
• Verification of kernel patches and system updates required
• Monitoring network traffic for suspicious IPv6 packets necessary

Technical summary

The Linux kernel's seg6 implementation does not properly reset the IPv6 control block (IP6CB) after decapsulation of IPv6 packets. This can lead to an out-of-bounds read when the packet is processed by the IPv6 input path. An unprivileged user can exploit this vulnerability by injecting a specially crafted packet with Hop-by-Hop and Destination Options headers followed by an SRH and a minimal inner IPv6 packet.

Defensive priority

Medium

Recommended defensive actions

• Review and apply the provided kernel patches to ensure the seg6 vulnerability is addressed.
• Monitor network traffic for suspicious IPv6 packets that could be used to exploit this vulnerability.
• Verify that affected systems are updated with the latest kernel versions.
• 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.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.

Evidence notes

The vulnerability was resolved by resetting the IP6CB after IPv6 decapsulation. The fix involves saving the incoming interface index and L3 slave state before clearing IP6CB and restoring them afterward.

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.