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

Vulnerability from cvelistv5 – Published: 2026-04-13 13:40 – Updated: 2026-05-11 22:08
VLAI
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
References
Impacted products
Vendor Product Version
Linux 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)
Create a notification for this product.
Linux 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)
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sched/cls_fw.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "d6d5bd62a09650856e1e2010eb09853eba0d64e1",
              "status": "affected",
              "version": "1abf272022cf1d18469405f47b4ec49c6a3125db",
              "versionType": "git"
            },
            {
              "lessThan": "febf64ca79a2d6540ab6e5e197fa0f4f7e84473e",
              "status": "affected",
              "version": "1abf272022cf1d18469405f47b4ec49c6a3125db",
              "versionType": "git"
            },
            {
              "lessThan": "3d41f9a314afa94b1c7c7c75405920123220e8cd",
              "status": "affected",
              "version": "1abf272022cf1d18469405f47b4ec49c6a3125db",
              "versionType": "git"
            },
            {
              "lessThan": "18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28",
              "status": "affected",
              "version": "1abf272022cf1d18469405f47b4ec49c6a3125db",
              "versionType": "git"
            },
            {
              "lessThan": "5cf41031922c154aa5ccda8bcdb0f5e6226582ec",
              "status": "affected",
              "version": "1abf272022cf1d18469405f47b4ec49c6a3125db",
              "versionType": "git"
            },
            {
              "lessThan": "3cb055df9e8625ce699a259d8178d67b37f2b160",
              "status": "affected",
              "version": "1abf272022cf1d18469405f47b4ec49c6a3125db",
              "versionType": "git"
            },
            {
              "lessThan": "96426c348def662b06bfdc65be3002905604927a",
              "status": "affected",
              "version": "1abf272022cf1d18469405f47b4ec49c6a3125db",
              "versionType": "git"
            },
            {
              "lessThan": "faeea8bbf6e958bf3c00cb08263109661975987c",
              "status": "affected",
              "version": "1abf272022cf1d18469405f47b4ec49c6a3125db",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/sched/cls_fw.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.15"
            },
            {
              "lessThan": "4.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.253",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.203",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.168",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.134",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.81",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.22",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "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",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.22",
                  "versionStartIncluding": "4.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.12",
                  "versionStartIncluding": "4.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "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": "2026-05-11T22:08:22.956Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/d6d5bd62a09650856e1e2010eb09853eba0d64e1"
        },
        {
          "url": "https://git.kernel.org/stable/c/febf64ca79a2d6540ab6e5e197fa0f4f7e84473e"
        },
        {
          "url": "https://git.kernel.org/stable/c/3d41f9a314afa94b1c7c7c75405920123220e8cd"
        },
        {
          "url": "https://git.kernel.org/stable/c/18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28"
        },
        {
          "url": "https://git.kernel.org/stable/c/5cf41031922c154aa5ccda8bcdb0f5e6226582ec"
        },
        {
          "url": "https://git.kernel.org/stable/c/3cb055df9e8625ce699a259d8178d67b37f2b160"
        },
        {
          "url": "https://git.kernel.org/stable/c/96426c348def662b06bfdc65be3002905604927a"
        },
        {
          "url": "https://git.kernel.org/stable/c/faeea8bbf6e958bf3c00cb08263109661975987c"
        }
      ],
      "title": "net/sched: cls_fw: fix NULL pointer dereference on shared blocks",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31421",
    "datePublished": "2026-04-13T13:40:25.278Z",
    "dateReserved": "2026-03-09T15:48:24.088Z",
    "dateUpdated": "2026-05-11T22:08:22.956Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-31421",
      "date": "2026-05-27",
      "epss": "0.00015",
      "percentile": "0.0347"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-31421\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-04-13T14:16:11.740\",\"lastModified\":\"2026-05-20T18:10:34.707\",\"vulnStatus\":\"Analyzed\",\"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)\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":5.5,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":3.6}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-476\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"4.15\",\"versionEndExcluding\":\"5.10.253\",\"matchCriteriaId\":\"202FFB00-4CA7-44CB-ACA1-E88A2BF2264B\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.11\",\"versionEndExcluding\":\"5.15.203\",\"matchCriteriaId\":\"20DDB3E9-AABF-4107-ADB0-5362AA067045\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.16\",\"versionEndExcluding\":\"6.1.168\",\"matchCriteriaId\":\"E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.2\",\"versionEndExcluding\":\"6.6.134\",\"matchCriteriaId\":\"F56F925B-BAF8-4F4B-B62F-1496AF19A307\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.7\",\"versionEndExcluding\":\"6.12.81\",\"matchCriteriaId\":\"6EF80433-B33B-43C5-8E64-0FA7B8DCE1BC\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.13\",\"versionEndExcluding\":\"6.18.22\",\"matchCriteriaId\":\"C9DF8BCE-36D3-475D-9D21-19E4F02F9029\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.19\",\"versionEndExcluding\":\"6.19.12\",\"matchCriteriaId\":\"0A2B9540-02D5-41B4-B16A-82AF66FD4F36\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*\",\"matchCriteriaId\":\"F253B622-8837-4245-BCE5-A7BF8FC76A16\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*\",\"matchCriteriaId\":\"4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*\",\"matchCriteriaId\":\"F666C8D8-6538-46D4-B318-87610DE64C34\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*\",\"matchCriteriaId\":\"02259FDA-961B-47BC-AE7F-93D7EC6E90C2\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*\",\"matchCriteriaId\":\"58A9FEFF-C040-420D-8F0A-BFDAAA1DF258\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*\",\"matchCriteriaId\":\"1D2315C0-D46F-4F85-9754-F9E5E11374A6\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/3cb055df9e8625ce699a259d8178d67b37f2b160\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/3d41f9a314afa94b1c7c7c75405920123220e8cd\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/5cf41031922c154aa5ccda8bcdb0f5e6226582ec\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/96426c348def662b06bfdc65be3002905604927a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/d6d5bd62a09650856e1e2010eb09853eba0d64e1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/faeea8bbf6e958bf3c00cb08263109661975987c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/febf64ca79a2d6540ab6e5e197fa0f4f7e84473e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}"
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.