CVE-2026-99041None▾ SunlitIn the Linux kernel, the following vulnerability has been resolved: ip6_gre: remove obsolete ERSPAN PMTU update A tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb, and mirred can redirect it to a native ip6erspan devi…
▾ Sunlit zone — Low / medium · no exploitation signal
impact 2.8 · likelihood 0 · exploitation 0
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In the Linux kernel, the following vulnerability has been resolved:
ip6_gre: remove obsolete ERSPAN PMTU update
A tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb, and mirred can redirect it to a native ip6erspan device. The legacy PMTU update in ip6erspan_tunnel_xmit() treats that metadata dst as a route. Since it has no output device, dst_dev(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: ip6erspan_tunnel_xmit+0x10fc/0x2cc0 Kernel panic - not syncing: Fatal exception in interrupt
The update is obsolete. Commit fe1a4ca0a2b7 ("ip6_gre: process toobig in a better way") changed IPv6 GRE Too Big handling to update the underlay route and removed the equivalent block from __gre6_xmit(). ip6_tnl_xmit() 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.
Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < b14a682ad7d45345701e08f9279d483a1da8b36cLinux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < f5b143f4cd3fb7673df8d727550478a4b762908aLinux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < 2d06cb25a497d3a7034ef9d172626c2d6620a0f1Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < 8f27260b989f488760289276377db24fbfb20bfaLinux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < 8bc60db48e8cba35488bbd6e1f94aa990afa275aLinux 4.16Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
Connected by shared product, vendor, weakness, or advisory.
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