ip6_gre: remove obsolete ERSPAN PMTU update

Summary

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RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0 Kernel panic - not syncing: Fatal exception in interrupt The update is obsolete.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.

Timeline

1. Oct 23, 2026, 12:22 PM UTCCVE published
2. Oct 23, 2026, 12:45 PM UTCFirst seen by cve.now
3. Oct 30, 2026, 12:41 PM UTCRecord last updated

Affected versions

• Linux Linux

  Version range not reported

• Linux Linux

  4.16

• KernelLinux

  From 4.16.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.114; From 6.13.0 · fixed in 6.18.58; From 6.19.0 · fixed in 7.2.11

References 7