UBUNTU-CVE-2026-99041: Medium severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: ip6gre: remove obsolete ERSPAN PMTU update A tc tunnelkey action can attach a METADATAIPTUNNEL dst to an skb, and mirred can redirect it to a native ip6erspan device. The legacy PMTU update in ip6erspantunnelxmit() treats that metadata dst as a route. Since it has no output device, dstdev(dst)->mtu dereferences NULL. On v7.2 with KASAN, an initial UID/GID 65534 process with CapEff 0 used self-created user and network namespaces to trigger: KASAN: null-ptr-deref RIP: ip6erspantunnelxmit+0x10fc/0x2cc0 Kernel panic - not syncing: Fatal exception in interrupt The update is obsolete. Commit fe1a4ca0a2b7 ("ip6gre: process toobig in a better way") changed IPv6 GRE Too Big handling to update the underlay route and removed the equivalent block from gre6xmit(). ip6tnlxmit() then propagates the underlay PMTU to the overlay route. Remove the stale ERSPAN copy and its now-unused dst variable. This eliminates the metadata-dst dereference and keeps ERSPAN aligned with IPv6 GRE PMTU handling.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.18~24.04.1 - Upgrade
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ubuntu/linux-azure-fde-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1019.19~24.04.1 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.19~24.04.1 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1016.18~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-43.43.1~24.04.2 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.3.0-10.10 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.3.0-1004.4 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.3.0-1004.4 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.3.0-1004.5 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.3.0-1004.4 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.3.0-1004.4 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 7.3.0-1004.4 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.3.0-10.10.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.3.0-10.10.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-43.43 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1017.18 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1020.21 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1019.19 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1017.19 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1010.11 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1018.18 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1018.18 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-43.43.1
Event History
Frequently Asked Questions
What conditions are needed to trigger the crash?
The trigger requires a tc tunnel_key action to attach METADATA_IP_TUNNEL metadata to a packet and a mirred action to redirect that packet to a native ip6erspan device. The failure occurs when the ERSPAN transmit path treats the metadata destination as a route and dereferences its missing output device.
Can an unprivileged process trigger this?
The reported reproduction used a process with UID/GID 65534 and no effective capabilities. It created its own user and network namespaces before triggering the issue.
What is the observed impact?
The reported result is a NULL-pointer dereference in ip6erspan_tunnel_xmit(), followed by a kernel panic. This can cause a denial of service on the affected system.