Vulnerability-Lookup

GHSA-P22X-MPCM-2H5H

Vulnerability from github – Published: 2026-10-23 15:31 – Updated: 2026-10-23 15:31

Details

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The update is obsolete.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.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-99041"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-23T13:17:27Z",
    "severity": null
  },
  "details": "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 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)-\u003emtu 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 RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nThe update is obsolete.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.",
  "id": "GHSA-p22x-mpcm-2h5h",
  "modified": "2026-10-23T15:31:36Z",
  "published": "2026-10-23T15:31:36Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99041"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2d06cb25a497d3a7034ef9d172626c2d6620a0f1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8bc60db48e8cba35488bbd6e1f94aa990afa275a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8f27260b989f488760289276377db24fbfb20bfa"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b14a682ad7d45345701e08f9279d483a1da8b36c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f5b143f4cd3fb7673df8d727550478a4b762908a"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-99041 (GCVE-0-2026-99041)

Vulnerability from cvelistv5 – Published: 2026-10-23 12:22 – Updated: 2026-10-23 12:22

Title

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.

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 7056 records in the last 180 days details

References

5 references

URL	Tags
https://git.kernel.org/stable/c/b14a682ad7d453457…
https://git.kernel.org/stable/c/f5b143f4cd3fb7673…
https://git.kernel.org/stable/c/2d06cb25a497d3a70…
https://git.kernel.org/stable/c/8f27260b989f48876…
https://git.kernel.org/stable/c/8bc60db48e8cba354…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 5a963eb61b7c39e6c422b6e48619d19d04719358 , < b14a682ad7d45345701e08f9279d483a1da8b36c (git) Affected: 5a963eb61b7c39e6c422b6e48619d19d04719358 , < f5b143f4cd3fb7673df8d727550478a4b762908a (git) Affected: 5a963eb61b7c39e6c422b6e48619d19d04719358 , < 2d06cb25a497d3a7034ef9d172626c2d6620a0f1 (git) Affected: 5a963eb61b7c39e6c422b6e48619d19d04719358 , < 8f27260b989f488760289276377db24fbfb20bfa (git) Affected: 5a963eb61b7c39e6c422b6e48619d19d04719358 , < 8bc60db48e8cba35488bbd6e1f94aa990afa275a (git)
Linux	Linux	Affected: 4.16 Unaffected: 0 , < 4.16 (semver) Unaffected: 6.6.160 , ≤ 6.6.* (semver) Unaffected: 6.12.114 , ≤ 6.12.* (semver) Unaffected: 6.18.58 , ≤ 6.18.* (semver) Unaffected: 7.2.11 , ≤ 7.2.* (semver) Unaffected: 7.3 , ≤ * (original_commit_for_fix)

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{
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ip6_gre.c"
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              "versionType": "git"
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          "product": "Linux",
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          "versions": [
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              "status": "unaffected",
              "version": "0",
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              "status": "unaffected",
              "version": "6.18.58",
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            },
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              "status": "unaffected",
              "version": "7.2.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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          "url": "https://git.kernel.org/stable/c/8f27260b989f488760289276377db24fbfb20bfa"
        },
        {
          "url": "https://git.kernel.org/stable/c/8bc60db48e8cba35488bbd6e1f94aa990afa275a"
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      "title": "ip6_gre: remove obsolete ERSPAN PMTU update",
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    "cveId": "CVE-2026-99041",
    "datePublished": "2026-10-23T12:22:00.403Z",
    "dateReserved": "2026-09-25T10:25:14.387Z",
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  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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