{"id":"CVE-2026-99041","title":"ip6_gre: remove obsolete ERSPAN PMTU update","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nip6_gre: remove obsolete ERSPAN PMTU update\n\nA tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb,\nand mirred can redirect it to a native ip6erspan devi…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < b14a682ad7d45345701e08f9279d483a1da8b36c","Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < f5b143f4cd3fb7673df8d727550478a4b762908a","Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < 2d06cb25a497d3a7034ef9d172626c2d6620a0f1","Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < 8f27260b989f488760289276377db24fbfb20bfa","Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < 8bc60db48e8cba35488bbd6e1f94aa990afa275a","Linux 4.16"],"published":"2026-10-23","updated":"2026-10-23","sourceUpdated":"2026-10-23T12:22:00.403Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99041","references":[{"url":"https://git.kernel.org/stable/c/b14a682ad7d45345701e08f9279d483a1da8b36c"},{"url":"https://git.kernel.org/stable/c/f5b143f4cd3fb7673df8d727550478a4b762908a"},{"url":"https://git.kernel.org/stable/c/2d06cb25a497d3a7034ef9d172626c2d6620a0f1"},{"url":"https://git.kernel.org/stable/c/8f27260b989f488760289276377db24fbfb20bfa"},{"url":"https://git.kernel.org/stable/c/8bc60db48e8cba35488bbd6e1f94aa990afa275a"}],"tags":["cve.org"],"ingestedAt":"2026-10-23T13:24:55.526Z","slug":"CVE-2026-99041","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nip6_gre: remove obsolete ERSPAN PMTU update\n\nA tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb,\nand mirred can redirect it to a native ip6erspan device. The legacy PMTU\nupdate in ip6erspan_tunnel_xmit() treats that metadata dst as a route.\nSince it has no output device, dst_dev(dst)->mtu dereferences NULL.\n\nOn v7.2 with KASAN, an initial UID/GID 65534 process with CapEff 0 used\nself-created user and network namespaces to trigger:\n\n  KASAN: null-ptr-deref\n  RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nThe update is obsolete. Commit fe1a4ca0a2b7 (\"ip6_gre: process toobig\nin a better way\") changed IPv6 GRE Too Big handling to update the\nunderlay route and removed the equivalent block from __gre6_xmit().\nip6_tnl_xmit() then propagates the underlay PMTU to the overlay route.\n\nRemove the stale ERSPAN copy and its now-unused dst variable. This\neliminates the metadata-dst dereference and keeps ERSPAN aligned with\nIPv6 GRE PMTU handling.\n\n## Affected\n\n- `Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < b14a682ad7d45345701e08f9279d483a1da8b36c`\n- `Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < f5b143f4cd3fb7673df8d727550478a4b762908a`\n- `Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < 2d06cb25a497d3a7034ef9d172626c2d6620a0f1`\n- `Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < 8f27260b989f488760289276377db24fbfb20bfa`\n- `Linux >= 5a963eb61b7c39e6c422b6e48619d19d04719358 < 8bc60db48e8cba35488bbd6e1f94aa990afa275a`\n- `Linux 4.16`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}