Vulnerability-Lookup

CVE-2026-31421 (GCVE-0-2026-31421)

Vulnerability from cvelistv5 – Published: 2026-04-13 13:40 – Updated: 2026-04-18 08:59

Title

net/sched: cls_fw: fix NULL pointer dereference on shared blocks

Summary

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_fw: fix NULL pointer dereference on shared blocks The old-method path in fw_classify() calls tcf_block_q() and dereferences q->handle. Shared blocks leave block->q NULL, causing a NULL deref when an empty cls_fw filter is attached to a shared block and a packet with a nonzero major skb mark is classified. Reject the configuration in fw_change() when the old method (no TCA_OPTIONS) is used on a shared block, since fw_classify()'s old-method path needs block->q which is NULL for shared blocks. The fixed null-ptr-deref calling stack: KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:fw_classify (net/sched/cls_fw.c:81) Call Trace: tcf_classify (./include/net/tc_wrapper.h:197 net/sched/cls_api.c:1764 net/sched/cls_api.c:1860) tc_run (net/core/dev.c:4401) __dev_queue_xmit (net/core/dev.c:4535 net/core/dev.c:4790)

Severity ?

No CVSS data available.

Assigner

Linux

References

URL

Tags

	https://git.kernel.org/stable/c/d6d5bd62a09650856…
	https://git.kernel.org/stable/c/febf64ca79a2d6540…
	https://git.kernel.org/stable/c/3d41f9a314afa94b1…
	https://git.kernel.org/stable/c/18328eff2f97d1a6a…
	https://git.kernel.org/stable/c/5cf41031922c154aa…
	https://git.kernel.org/stable/c/3cb055df9e8625ce6…
	https://git.kernel.org/stable/c/96426c348def662b0…
	https://git.kernel.org/stable/c/faeea8bbf6e958bf3…

Impacted products

Vendor

Product

Version

Linux

Affected: 1abf272022cf1d18469405f47b4ec49c6a3125db , < d6d5bd62a09650856e1e2010eb09853eba0d64e1 (git)
Affected: 1abf272022cf1d18469405f47b4ec49c6a3125db , < febf64ca79a2d6540ab6e5e197fa0f4f7e84473e (git)
Affected: 1abf272022cf1d18469405f47b4ec49c6a3125db , < 3d41f9a314afa94b1c7c7c75405920123220e8cd (git)
Affected: 1abf272022cf1d18469405f47b4ec49c6a3125db , < 18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28 (git)
Affected: 1abf272022cf1d18469405f47b4ec49c6a3125db , < 5cf41031922c154aa5ccda8bcdb0f5e6226582ec (git)
Affected: 1abf272022cf1d18469405f47b4ec49c6a3125db , < 3cb055df9e8625ce699a259d8178d67b37f2b160 (git)
Affected: 1abf272022cf1d18469405f47b4ec49c6a3125db , < 96426c348def662b06bfdc65be3002905604927a (git)
Affected: 1abf272022cf1d18469405f47b4ec49c6a3125db , < faeea8bbf6e958bf3c00cb08263109661975987c (git)

Linux

Affected: 4.15
Unaffected: 0 , < 4.15 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.168 , ≤ 6.1.* (semver)
Unaffected: 6.6.134 , ≤ 6.6.* (semver)
Unaffected: 6.12.81 , ≤ 6.12.* (semver)
Unaffected: 6.18.22 , ≤ 6.18.* (semver)
Unaffected: 6.19.12 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sched/cls_fw.c"
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          "vendor": "Linux",
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              "version": "4.15"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "status": "unaffected",
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              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "5.15.203",
              "versionType": "semver"
            },
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              "status": "unaffected",
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              "versionType": "semver"
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.12.81",
              "versionType": "semver"
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.22",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.12",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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          "nodes": [
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                  "versionEndExcluding": "5.10.253",
                  "versionStartIncluding": "4.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.203",
                  "versionStartIncluding": "4.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.168",
                  "versionStartIncluding": "4.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.134",
                  "versionStartIncluding": "4.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.81",
                  "versionStartIncluding": "4.15",
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                {
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                  "versionStartIncluding": "4.15",
                  "vulnerable": true
                },
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                  "versionEndExcluding": "7.0",
                  "versionStartIncluding": "4.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_fw: fix NULL pointer dereference on shared blocks\n\nThe old-method path in fw_classify() calls tcf_block_q() and\ndereferences q-\u003ehandle.  Shared blocks leave block-\u003eq NULL, causing a\nNULL deref when an empty cls_fw filter is attached to a shared block\nand a packet with a nonzero major skb mark is classified.\n\nReject the configuration in fw_change() when the old method (no\nTCA_OPTIONS) is used on a shared block, since fw_classify()\u0027s\nold-method path needs block-\u003eq which is NULL for shared blocks.\n\nThe fixed null-ptr-deref calling stack:\n KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]\n RIP: 0010:fw_classify (net/sched/cls_fw.c:81)\n Call Trace:\n  tcf_classify (./include/net/tc_wrapper.h:197 net/sched/cls_api.c:1764 net/sched/cls_api.c:1860)\n  tc_run (net/core/dev.c:4401)\n  __dev_queue_xmit (net/core/dev.c:4535 net/core/dev.c:4790)"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-18T08:59:33.538Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/d6d5bd62a09650856e1e2010eb09853eba0d64e1"
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          "url": "https://git.kernel.org/stable/c/febf64ca79a2d6540ab6e5e197fa0f4f7e84473e"
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        },
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        },
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          "url": "https://git.kernel.org/stable/c/faeea8bbf6e958bf3c00cb08263109661975987c"
        }
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    "cveId": "CVE-2026-31421",
    "datePublished": "2026-04-13T13:40:25.278Z",
    "dateReserved": "2026-03-09T15:48:24.088Z",
    "dateUpdated": "2026-04-18T08:59:33.538Z",
    "state": "PUBLISHED"
  },
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      "cve": "CVE-2026-31421",
      "date": "2026-04-19",
      "epss": "0.00032",
      "percentile": "0.09068"
    },
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  }
}

FKIE_CVE-2026-31421

Vulnerability from fkie_nvd - Published: 2026-04-13 14:16 - Updated: 2026-04-18 09:16

Severity ?

Summary

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3cb055df9e8625ce699a259d8178d67b37f2b160
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3d41f9a314afa94b1c7c7c75405920123220e8cd
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/5cf41031922c154aa5ccda8bcdb0f5e6226582ec
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/96426c348def662b06bfdc65be3002905604927a
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/d6d5bd62a09650856e1e2010eb09853eba0d64e1
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/faeea8bbf6e958bf3c00cb08263109661975987c
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/febf64ca79a2d6540ab6e5e197fa0f4f7e84473e

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_fw: fix NULL pointer dereference on shared blocks\n\nThe old-method path in fw_classify() calls tcf_block_q() and\ndereferences q-\u003ehandle.  Shared blocks leave block-\u003eq NULL, causing a\nNULL deref when an empty cls_fw filter is attached to a shared block\nand a packet with a nonzero major skb mark is classified.\n\nReject the configuration in fw_change() when the old method (no\nTCA_OPTIONS) is used on a shared block, since fw_classify()\u0027s\nold-method path needs block-\u003eq which is NULL for shared blocks.\n\nThe fixed null-ptr-deref calling stack:\n KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]\n RIP: 0010:fw_classify (net/sched/cls_fw.c:81)\n Call Trace:\n  tcf_classify (./include/net/tc_wrapper.h:197 net/sched/cls_api.c:1764 net/sched/cls_api.c:1860)\n  tc_run (net/core/dev.c:4401)\n  __dev_queue_xmit (net/core/dev.c:4535 net/core/dev.c:4790)"
    }
  ],
  "id": "CVE-2026-31421",
  "lastModified": "2026-04-18T09:16:31.920",
  "metrics": {},
  "published": "2026-04-13T14:16:11.740",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28"
    },
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3cb055df9e8625ce699a259d8178d67b37f2b160"
    },
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      "url": "https://git.kernel.org/stable/c/3d41f9a314afa94b1c7c7c75405920123220e8cd"
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      "url": "https://git.kernel.org/stable/c/d6d5bd62a09650856e1e2010eb09853eba0d64e1"
    },
    {
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    },
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      "url": "https://git.kernel.org/stable/c/febf64ca79a2d6540ab6e5e197fa0f4f7e84473e"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}

GHSA-PMQM-G7JM-76HF

Vulnerability from github – Published: 2026-04-13 15:31 – Updated: 2026-04-18 09:30

Details

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

net/sched: cls_fw: fix NULL pointer dereference on shared blocks

The old-method path in fw_classify() calls tcf_block_q() and dereferences q->handle. Shared blocks leave block->q NULL, causing a NULL deref when an empty cls_fw filter is attached to a shared block and a packet with a nonzero major skb mark is classified.

Reject the configuration in fw_change() when the old method (no TCA_OPTIONS) is used on a shared block, since fw_classify()'s old-method path needs block->q which is NULL for shared blocks.

The fixed null-ptr-deref calling stack: KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:fw_classify (net/sched/cls_fw.c:81) Call Trace: tcf_classify (./include/net/tc_wrapper.h:197 net/sched/cls_api.c:1764 net/sched/cls_api.c:1860) tc_run (net/core/dev.c:4401) __dev_queue_xmit (net/core/dev.c:4535 net/core/dev.c:4790)

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-31421"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-13T14:16:11Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_fw: fix NULL pointer dereference on shared blocks\n\nThe old-method path in fw_classify() calls tcf_block_q() and\ndereferences q-\u003ehandle.  Shared blocks leave block-\u003eq NULL, causing a\nNULL deref when an empty cls_fw filter is attached to a shared block\nand a packet with a nonzero major skb mark is classified.\n\nReject the configuration in fw_change() when the old method (no\nTCA_OPTIONS) is used on a shared block, since fw_classify()\u0027s\nold-method path needs block-\u003eq which is NULL for shared blocks.\n\nThe fixed null-ptr-deref calling stack:\n KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]\n RIP: 0010:fw_classify (net/sched/cls_fw.c:81)\n Call Trace:\n  tcf_classify (./include/net/tc_wrapper.h:197 net/sched/cls_api.c:1764 net/sched/cls_api.c:1860)\n  tc_run (net/core/dev.c:4401)\n  __dev_queue_xmit (net/core/dev.c:4535 net/core/dev.c:4790)",
  "id": "GHSA-pmqm-g7jm-76hf",
  "modified": "2026-04-18T09:30:20Z",
  "published": "2026-04-13T15:31:42Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31421"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3cb055df9e8625ce699a259d8178d67b37f2b160"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3d41f9a314afa94b1c7c7c75405920123220e8cd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5cf41031922c154aa5ccda8bcdb0f5e6226582ec"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/96426c348def662b06bfdc65be3002905604927a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d6d5bd62a09650856e1e2010eb09853eba0d64e1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/faeea8bbf6e958bf3c00cb08263109661975987c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/febf64ca79a2d6540ab6e5e197fa0f4f7e84473e"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

MSRC_CVE-2026-31421

Vulnerability from csaf_microsoft - Published: 2026-04-02 00:00 - Updated: 2026-04-18 14:40

Summary

net/sched: cls_fw: fix NULL pointer dereference on shared blocks

Notes

Additional Resources: To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle

Disclaimer: The information provided in the Microsoft Knowledge Base is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

CVE-2026-31421

Vendor Fix 6.6.134.1-1:Security Update:https://learn.microsoft.com/en-us/azure/azure-linux/tutorial-azure-linux-upgrade https://learn.microsoft.com/en-us/azure/azure-lin…

References

URL

Category

	https://msrc.microsoft.com/csaf/vex/2026/msrc_cve…	self
	https://support.microsoft.com/lifecycle	external
	https://www.first.org/cvss	external
	https://msrc.microsoft.com/csaf/vex/2026/msrc_cve…	self

JSON

To clipboard

{
  "document": {
    "category": "csaf_vex",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Public",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en-US",
    "notes": [
      {
        "category": "general",
        "text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
        "title": "Additional Resources"
      },
      {
        "category": "legal_disclaimer",
        "text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
        "title": "Disclaimer"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "secure@microsoft.com",
      "name": "Microsoft Security Response Center",
      "namespace": "https://msrc.microsoft.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "CVE-2026-31421 net/sched: cls_fw: fix NULL pointer dereference on shared blocks - VEX",
        "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-31421.json"
      },
      {
        "category": "external",
        "summary": "Microsoft Support Lifecycle",
        "url": "https://support.microsoft.com/lifecycle"
      },
      {
        "category": "external",
        "summary": "Common Vulnerability Scoring System",
        "url": "https://www.first.org/cvss"
      }
    ],
    "title": "net/sched: cls_fw: fix NULL pointer dereference on shared blocks",
    "tracking": {
      "current_release_date": "2026-04-18T14:40:24.000Z",
      "generator": {
        "date": "2026-04-19T07:19:01.468Z",
        "engine": {
          "name": "MSRC Generator",
          "version": "1.0"
        }
      },
      "id": "msrc_CVE-2026-31421",
      "initial_release_date": "2026-04-02T00:00:00.000Z",
      "revision_history": [
        {
          "date": "2026-04-14T01:02:33.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
        },
        {
          "date": "2026-04-18T14:40:24.000Z",
          "legacy_version": "2",
          "number": "2",
          "summary": "Information published."
        }
      ],
      "status": "final",
      "version": "2"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version",
                "name": "3.0",
                "product": {
                  "name": "Azure Linux 3.0",
                  "product_id": "17084"
                }
              }
            ],
            "category": "product_name",
            "name": "Azure Linux"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "\u003cazl3 kernel 6.6.130.1-3",
                "product": {
                  "name": "\u003cazl3 kernel 6.6.130.1-3",
                  "product_id": "1"
                }
              },
              {
                "category": "product_version",
                "name": "azl3 kernel 6.6.130.1-3",
                "product": {
                  "name": "azl3 kernel 6.6.130.1-3",
                  "product_id": "21094"
                }
              }
            ],
            "category": "product_name",
            "name": "kernel"
          }
        ],
        "category": "vendor",
        "name": "Microsoft"
      }
    ],
    "relationships": [
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "\u003cazl3 kernel 6.6.130.1-3 as a component of Azure Linux 3.0",
          "product_id": "17084-1"
        },
        "product_reference": "1",
        "relates_to_product_reference": "17084"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "azl3 kernel 6.6.130.1-3 as a component of Azure Linux 3.0",
          "product_id": "21094-17084"
        },
        "product_reference": "21094",
        "relates_to_product_reference": "17084"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-31421",
      "notes": [
        {
          "category": "general",
          "text": "Linux",
          "title": "Assigning CNA"
        }
      ],
      "product_status": {
        "fixed": [
          "21094-17084"
        ],
        "known_affected": [
          "17084-1"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-31421 net/sched: cls_fw: fix NULL pointer dereference on shared blocks - VEX",
          "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-31421.json"
        }
      ],
      "remediations": [
        {
          "category": "vendor_fix",
          "date": "2026-04-14T01:02:33.000Z",
          "details": "6.6.134.1-1:Security Update:https://learn.microsoft.com/en-us/azure/azure-linux/tutorial-azure-linux-upgrade",
          "product_ids": [
            "17084-1"
          ],
          "url": "https://learn.microsoft.com/en-us/azure/azure-linux/tutorial-azure-linux-upgrade"
        }
      ],
      "title": "net/sched: cls_fw: fix NULL pointer dereference on shared blocks"
    }
  ]
}

Sightings

Author	Source	Type	Date

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.

Action not permitted

CVE-2026-31421 (GCVE-0-2026-31421)

FKIE_CVE-2026-31421

GHSA-PMQM-G7JM-76HF

MSRC_CVE-2026-31421

Tags

Sightings

Nomenclature