CVE-2026-80996: net: l2tp: do not propagate multicast notification errors
In the Linux kernel, the following vulnerability has been resolved:
net: l2tp: do not propagate multicast notification errors
The tunnel create, tunnel modify, session create, and session modify netlink handlers send multicast notifications through helpers that can fail while allocating or encoding a message, or while multicasting it.
For tunnel and session create/modify, a notification is sent after the live operation has completed. Returning a best-effort notification error as the command result can therefore report failure for an operation that already committed and can cause callers to retry and accumulate live objects.
Keep sending notifications for listener visibility, but do not propagate their best-effort status as the command result. This also keeps the tunnel modify command consistent with the other notification-only paths.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.12.111-1 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 7.2.6-1 - Upgrade
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debian/linux-6.12to a version that resolves this vulnerability.Fixed in 6.12.111-1~deb12u1 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.1.191 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.6.160 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.12.109 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.18.50 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 7.2.4 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1 - Upgrade
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debian/linux-6.12to a version that resolves this vulnerability.Fixed in 6.12.113-1~deb12u1 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1
Event History
Frequently Asked Questions
What conditions can trigger the incorrect failure result?
It can occur when multicast notification delivery fails after an L2TP tunnel or session create or modify operation has already completed. The notification helpers can fail during message allocation, message encoding, or multicast delivery.
What is the practical impact on netlink clients?
A client can receive an error for a create or modify command even though the requested L2TP object or change is already live. If the client retries a reported failed create, it can accumulate additional live tunnel or session objects.
Are multicast listeners required for the underlying L2TP operation to succeed?
No. Multicast notifications are best-effort visibility mechanisms and should not determine the command result after the live operation has completed. The fix continues to send notifications but prevents notification failures from being returned to the caller.
How can operators identify possible prior impact?
Investigate cases where L2TP netlink create or modify requests returned errors and were retried. Compare the reported command failures with the actual existing tunnels and sessions, looking for objects or changes that were created despite an error response.