Vulnerability-Lookup

FKIE_CVE-2026-31680

Vulnerability from fkie_nvd - Published: 2026-04-25 09:16 - Updated: 2026-07-14 13:18

Severity

7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: net: ipv6: flowlabel: defer exclusive option free until RCU teardown `ip6fl_seq_show()` walks the global flowlabel hash under the seq-file RCU read-side lock and prints `fl->opt->opt_nflen` when an option block is present. Exclusive flowlabels currently free `fl->opt` as soon as `fl->users` drops to zero in `fl_release()`. However, the surrounding `struct ip6_flowlabel` remains visible in the global hash table until later garbage collection removes it and `fl_free_rcu()` finally tears it down. A concurrent `/proc/net/ip6_flowlabel` reader can therefore race that early `kfree()` and dereference freed option state, triggering a crash in `ip6fl_seq_show()`. Fix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches the lifetime already required for the enclosing flowlabel while readers can still reach it under RCU.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091	Patch
0b142b55-0307-4c5a-b3c9-f314f3fb7c5e	https://cert-portal.siemens.com/productcert/html/ssa-019113.html
0b142b55-0307-4c5a-b3c9-f314f3fb7c5e	https://cert-portal.siemens.com/productcert/html/ssa-082556.html

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ip6_flowlabel.c"
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              "version": "5.15.203",
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          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "vendor": "Siemens",
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              "versionType": "custom"
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        },
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          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "vendor": "Siemens",
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        },
        {
          "defaultStatus": "unknown",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "vendor": "Siemens",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "V3.1.6",
              "versionType": "custom"
            }
          ]
        },
        {
          "defaultStatus": "unknown",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "vendor": "Siemens",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "V3.1.5",
              "versionType": "custom"
            }
          ]
        },
        {
          "defaultStatus": "unknown",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "vendor": "Siemens",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "V3.1.6",
              "versionType": "custom"
            }
          ]
        },
        {
          "defaultStatus": "unknown",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "vendor": "Siemens",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "V3.1.5",
              "versionType": "custom"
            }
          ]
        },
        {
          "defaultStatus": "unknown",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "vendor": "Siemens",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "V3.1.6",
              "versionType": "custom"
            }
          ]
        },
        {
          "defaultStatus": "unknown",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "vendor": "Siemens",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "V3.1.5",
              "versionType": "custom"
            }
          ]
        },
        {
          "defaultStatus": "unknown",
          "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
          "vendor": "Siemens",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "V3.1.6",
              "versionType": "custom"
            }
          ]
        },
        {
          "defaultStatus": "unknown",
          "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
          "vendor": "Siemens",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "V3.1.5",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "A73B6C7F-59A9-4C13-93DA-043EF7196D2E",
              "versionEndExcluding": "5.10.253",
              "versionStartIncluding": "3.9",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045",
              "versionEndExcluding": "5.15.203",
              "versionStartIncluding": "5.11",
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            },
            {
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              "matchCriteriaId": "E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B",
              "versionEndExcluding": "6.1.168",
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            {
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            {
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            {
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              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*",
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            {
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              "vulnerable": true
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              "vulnerable": true
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          "negate": false,
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      ]
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: flowlabel: defer exclusive option free until RCU teardown\n\n`ip6fl_seq_show()` walks the global flowlabel hash under the seq-file\nRCU read-side lock and prints `fl-\u003eopt-\u003eopt_nflen` when an option block\nis present.\n\nExclusive flowlabels currently free `fl-\u003eopt` as soon as `fl-\u003eusers`\ndrops to zero in `fl_release()`. However, the surrounding\n`struct ip6_flowlabel` remains visible in the global hash table until\nlater garbage collection removes it and `fl_free_rcu()` finally tears it\ndown.\n\nA concurrent `/proc/net/ip6_flowlabel` reader can therefore race that\nearly `kfree()` and dereference freed option state, triggering a crash\nin `ip6fl_seq_show()`.\n\nFix this by keeping `fl-\u003eopt` alive until `fl_free_rcu()`. That matches\nthe lifetime already required for the enclosing flowlabel while readers\ncan still reach it under RCU."
    }
  ],
  "id": "CVE-2026-31680",
  "lastModified": "2026-07-14T13:18:48.493",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-04-25T09:16:01.673",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
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      "url": "https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091"
    },
    {
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
    },
    {
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}

CVE-2026-31680 (GCVE-0-2026-31680)

Vulnerability from cvelistv5 – Published: 2026-04-25 08:46 – Updated: 2026-09-08 08:48

Title

net: ipv6: flowlabel: defer exclusive option free until RCU teardown

Summary

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

10 references

URL	Tags
https://git.kernel.org/stable/c/4b6798024f7b2d535…
https://git.kernel.org/stable/c/3c54b66c83fb8fcbd…
https://git.kernel.org/stable/c/5a6b15f861b7c1304…
https://git.kernel.org/stable/c/6c7fbdb8ffde64136…
https://git.kernel.org/stable/c/8027964931785cb73…
https://git.kernel.org/stable/c/414726b69921fe635…
https://git.kernel.org/stable/c/572ce62778519a7d4…
https://git.kernel.org/stable/c/9ca562bb8e66978b5…
https://cert-portal.siemens.com/productcert/html/…
https://cert-portal.siemens.com/productcert/html/…

Impacted products

8 products

Vendor	Product	Version
Linux	Linux	Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 4b6798024f7b2d535f3db1002c760143cdbd1bd3 (git) Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 3c54b66c83fb8fcbde8e6a7bf90b65856e39f827 (git) Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 5a6b15f861b7c1304949e3350d23490a5fe429fd (git) Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 6c7fbdb8ffde6413640de7cfbd7c976c353e89f8 (git) Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 8027964931785cb73d520ac70a342a3dc16c249b (git) Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 414726b69921fe6355ae453f5b35e68dd078342a (git) Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 572ce62778519a7d4d1c15f55dd2e45a474133c4 (git) Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 9ca562bb8e66978b53028fa32b1a190708e6a091 (git)
Linux	Linux	Affected: 3.9 Unaffected: 0 , < 3.9 (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)
Siemens	SIMATIC S7-1500 CPU 1518-4 PN/DP MFP	Affected: V3.1.6 , < * (custom)
Siemens	SIMATIC S7-1500 CPU 1518-4 PN/DP MFP	Affected: V3.1.5 , < * (custom)
Siemens	SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP	Affected: V3.1.6 , < * (custom)
Siemens	SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP	Affected: V3.1.5 , < * (custom)
Siemens	SIPLUS S7-1500 CPU 1518-4 PN/DP MFP	Affected: V3.1.6 , < * (custom)
Siemens	SIPLUS S7-1500 CPU 1518-4 PN/DP MFP	Affected: V3.1.5 , < * (custom)

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{
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          "orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
          "shortName": "siemens-SADP"
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        "references": [
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            "url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
          },
          {
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          }
        ],
        "x_adpType": "supplier"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ip6_flowlabel.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499",
              "versionType": "git"
            },
            {
              "lessThan": "3c54b66c83fb8fcbde8e6a7bf90b65856e39f827",
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            {
              "lessThan": "5a6b15f861b7c1304949e3350d23490a5fe429fd",
              "status": "affected",
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          "vendor": "Linux",
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              "version": "3.9"
            },
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              "version": "0",
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              "versionType": "semver"
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            {
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              "status": "unaffected",
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              "versionType": "semver"
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              "versionType": "semver"
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              "version": "6.6.134",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.81",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "6.18.22",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "6.19.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
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        }
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      "cpeApplicability": [
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                  "versionEndExcluding": "5.10.253",
                  "versionStartIncluding": "3.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.203",
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                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "6.1.168",
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                {
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: flowlabel: defer exclusive option free until RCU teardown\n\n`ip6fl_seq_show()` walks the global flowlabel hash under the seq-file\nRCU read-side lock and prints `fl-\u003eopt-\u003eopt_nflen` when an option block\nis present.\n\nExclusive flowlabels currently free `fl-\u003eopt` as soon as `fl-\u003eusers`\ndrops to zero in `fl_release()`. However, the surrounding\n`struct ip6_flowlabel` remains visible in the global hash table until\nlater garbage collection removes it and `fl_free_rcu()` finally tears it\ndown.\n\nA concurrent `/proc/net/ip6_flowlabel` reader can therefore race that\nearly `kfree()` and dereference freed option state, triggering a crash\nin `ip6fl_seq_show()`.\n\nFix this by keeping `fl-\u003eopt` alive until `fl_free_rcu()`. That matches\nthe lifetime already required for the enclosing flowlabel while readers\ncan still reach it under RCU."
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            "baseSeverity": "HIGH",
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            "version": "3.1"
          },
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              "value": "AV:L - The vulnerable path is local: an attacker creates/releases IPv6 flowlabels through setsockopt(IPV6_FLOWLABEL_MGR) while reading /proc/net/ip6_flowlabel. Remote IPv6 packets do not reach this flowlabel option lifetime bug.\nAC:L - The race is between two attacker-controlled operations: flowlabel release and procfs seq-file reading. The attacker can run both sides concurrently and repeat the race without relying on external conditions.\nPR:L - Supplying the needed IPv6 option state commonly requires CAP_NET_RAW, but the check is against the socket network namespace user_ns and is reachable with low privileges via user namespaces. No real init-namespace root/admin privilege is required in the highest reasonable deployment scenario.\nUI:N - The attacker can create the socket state, release it, and read /proc/net/ip6_flowlabel directly. No victim action is required.\nS:U - This is a kernel memory lifetime bug within the same host kernel security authority. It does not cross a VM, IOMMU, or separate authorization boundary.\nC:H - The bug is a use-after-free of struct ipv6_txoptions reachable from procfs output, and freed kernel heap contents can be exposed or attacker-shaped. Per the required conservative guidance, kernel UAFs are scored High for confidentiality.\nI:H - Although the observed dereference is a stale read, this is a kernel heap use-after-free in attacker-reclaimable memory. Per the required conservative guidance and upward scoring on uncertainty, UAFs are scored High for integrity.\nA:H - A concurrent /proc/net/ip6_flowlabel reader can dereference freed option state in ip6fl_seq_show(), causing an oops or kernel crash. Kernel crashes are High availability impact."
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        }
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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          "url": "https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827"
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        {
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        {
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      ],
      "title": "net: ipv6: flowlabel: defer exclusive option free until RCU teardown",
      "x_generator": {
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31680",
    "datePublished": "2026-04-25T08:46:56.807Z",
    "dateReserved": "2026-03-09T15:48:24.130Z",
    "dateUpdated": "2026-09-08T08:48:05.243Z",
    "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.
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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.

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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FKIE_CVE-2026-31680

CVE-2026-31680 (GCVE-0-2026-31680)

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