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GHSA-2MGG-C98J-9PMM

Vulnerability from github – Published: 2026-08-10 15:33 – Updated: 2026-08-10 15:33

Details

In the Linux kernel, the following vulnerability has been resolved:

net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM

Before commit 00d066a4d4ed ("netdev_features: convert NETIF_F_LLTX to dev->lltx"), NETIF_F_LLTX was set unconditionally in both __gre_tunnel_init() and ip6gre_tnl_init_features() alongside GRE_FEATURES:

dev->features |= GRE_FEATURES | NETIF_F_LLTX;

When that commit converted NETIF_F_LLTX to the dev->lltx flag, it placed 'dev->lltx = true' after the SEQ/CSUM early returns instead of before them. This causes GRE/GRETAP/ip6gre tunnels with SEQ or CSUM+encap to lose lockless TX, reintroducing _xmit_lock acquisition around their ndo_start_xmit. Since GRE xmit re-enters the stack via ip_tunnel_xmit(), holding _xmit_lock risks ABBA deadlock with the underlay device.

CPU0 CPU1 ---- ---- lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3); lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3);

Fix by moving dev->lltx = true before the early returns in both functions, restoring the original unconditional behavior.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-68296"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-10T13:20:19Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: gre: fix lltx regression for GRE tunnels with SEQ/CSUM\n\nBefore commit 00d066a4d4ed (\"netdev_features: convert NETIF_F_LLTX to\ndev-\u003elltx\"), NETIF_F_LLTX was set unconditionally in both\n__gre_tunnel_init() and ip6gre_tnl_init_features() alongside\nGRE_FEATURES:\n\n    dev-\u003efeatures |= GRE_FEATURES | NETIF_F_LLTX;\n\nWhen that commit converted NETIF_F_LLTX to the dev-\u003elltx flag, it\nplaced \u0027dev-\u003elltx = true\u0027 after the SEQ/CSUM early returns instead\nof before them. This causes GRE/GRETAP/ip6gre tunnels with SEQ or\nCSUM+encap to lose lockless TX, reintroducing _xmit_lock acquisition\naround their ndo_start_xmit. Since GRE xmit re-enters the stack via\nip_tunnel_xmit(), holding _xmit_lock risks ABBA deadlock with the\nunderlay device.\n\n  CPU0                        CPU1\n  ----                        ----\n  lock(\u0026qdisc_xmit_lock_key#6);\n                              lock(\u0026qdisc_xmit_lock_key#3);\n                              lock(\u0026qdisc_xmit_lock_key#6);\n  lock(\u0026qdisc_xmit_lock_key#3);\n\nFix by moving dev-\u003elltx = true before the early returns in both\nfunctions, restoring the original unconditional behavior.",
  "id": "GHSA-2mgg-c98j-9pmm",
  "modified": "2026-08-10T15:33:45Z",
  "published": "2026-08-10T15:33:45Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68296"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2bffe379023512d280337c70faeb6a8cc435db5e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/675ed582c1aa4d919dd535490de08c015005c653"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9f948e9aede9678f4103457daf2bc9dd54c65a06"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-68296 (GCVE-0-2026-68296)

Vulnerability from cvelistv5 – Published: 2026-08-10 12:02 – Updated: 2026-08-17 05:02

Title

net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM

Summary

In the Linux kernel, the following vulnerability has been resolved: net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM Before commit 00d066a4d4ed ("netdev_features: convert NETIF_F_LLTX to dev->lltx"), NETIF_F_LLTX was set unconditionally in both __gre_tunnel_init() and ip6gre_tnl_init_features() alongside GRE_FEATURES: dev->features |= GRE_FEATURES | NETIF_F_LLTX; When that commit converted NETIF_F_LLTX to the dev->lltx flag, it placed 'dev->lltx = true' after the SEQ/CSUM early returns instead of before them. This causes GRE/GRETAP/ip6gre tunnels with SEQ or CSUM+encap to lose lockless TX, reintroducing _xmit_lock acquisition around their ndo_start_xmit. Since GRE xmit re-enters the stack via ip_tunnel_xmit(), holding _xmit_lock risks ABBA deadlock with the underlay device. CPU0 CPU1 ---- ---- lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3); lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3); Fix by moving dev->lltx = true before the early returns in both functions, restoring the original unconditional behavior.

Severity

No CVSS data available.

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/9f948e9aede9678f4…
https://git.kernel.org/stable/c/15a1c5f2ed2eeb3da…
https://git.kernel.org/stable/c/2bffe379023512d28…
https://git.kernel.org/stable/c/675ed582c1aa4d919…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 00d066a4d4edbe559ba6c35153da71d4b2b8a383 , < 9f948e9aede9678f4103457daf2bc9dd54c65a06 (git) Affected: 00d066a4d4edbe559ba6c35153da71d4b2b8a383 , < 15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3 (git) Affected: 00d066a4d4edbe559ba6c35153da71d4b2b8a383 , < 2bffe379023512d280337c70faeb6a8cc435db5e (git) Affected: 00d066a4d4edbe559ba6c35153da71d4b2b8a383 , < 675ed582c1aa4d919dd535490de08c015005c653 (git)
Linux	Linux	Affected: 6.12 Unaffected: 0 , < 6.12 (semver) Unaffected: 6.12.101 , ≤ 6.12.* (semver) Unaffected: 6.18.42 , ≤ 6.18.* (semver) Unaffected: 7.1.6 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/ip_gre.c",
            "net/ipv6/ip6_gre.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "9f948e9aede9678f4103457daf2bc9dd54c65a06",
              "status": "affected",
              "version": "00d066a4d4edbe559ba6c35153da71d4b2b8a383",
              "versionType": "git"
            },
            {
              "lessThan": "15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3",
              "status": "affected",
              "version": "00d066a4d4edbe559ba6c35153da71d4b2b8a383",
              "versionType": "git"
            },
            {
              "lessThan": "2bffe379023512d280337c70faeb6a8cc435db5e",
              "status": "affected",
              "version": "00d066a4d4edbe559ba6c35153da71d4b2b8a383",
              "versionType": "git"
            },
            {
              "lessThan": "675ed582c1aa4d919dd535490de08c015005c653",
              "status": "affected",
              "version": "00d066a4d4edbe559ba6c35153da71d4b2b8a383",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/ip_gre.c",
            "net/ipv6/ip6_gre.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.12"
            },
            {
              "lessThan": "6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.101",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.42",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.101",
                  "versionStartIncluding": "6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.42",
                  "versionStartIncluding": "6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "6.12",
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: gre: fix lltx regression for GRE tunnels with SEQ/CSUM\n\nBefore commit 00d066a4d4ed (\"netdev_features: convert NETIF_F_LLTX to\ndev-\u003elltx\"), NETIF_F_LLTX was set unconditionally in both\n__gre_tunnel_init() and ip6gre_tnl_init_features() alongside\nGRE_FEATURES:\n\n    dev-\u003efeatures |= GRE_FEATURES | NETIF_F_LLTX;\n\nWhen that commit converted NETIF_F_LLTX to the dev-\u003elltx flag, it\nplaced \u0027dev-\u003elltx = true\u0027 after the SEQ/CSUM early returns instead\nof before them. This causes GRE/GRETAP/ip6gre tunnels with SEQ or\nCSUM+encap to lose lockless TX, reintroducing _xmit_lock acquisition\naround their ndo_start_xmit. Since GRE xmit re-enters the stack via\nip_tunnel_xmit(), holding _xmit_lock risks ABBA deadlock with the\nunderlay device.\n\n  CPU0                        CPU1\n  ----                        ----\n  lock(\u0026qdisc_xmit_lock_key#6);\n                              lock(\u0026qdisc_xmit_lock_key#3);\n                              lock(\u0026qdisc_xmit_lock_key#6);\n  lock(\u0026qdisc_xmit_lock_key#3);\n\nFix by moving dev-\u003elltx = true before the early returns in both\nfunctions, restoring the original unconditional behavior."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:02:32.404Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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        },
        {
          "url": "https://git.kernel.org/stable/c/2bffe379023512d280337c70faeb6a8cc435db5e"
        },
        {
          "url": "https://git.kernel.org/stable/c/675ed582c1aa4d919dd535490de08c015005c653"
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      ],
      "title": "net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68296",
    "datePublished": "2026-08-10T12:02:29.464Z",
    "dateReserved": "2026-07-30T09:28:09.380Z",
    "dateUpdated": "2026-08-17T05:02:32.404Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
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.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

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GHSA-2MGG-C98J-9PMM

CVE-2026-68296 (GCVE-0-2026-68296)

Tags

Sightings

Nomenclature