CVE-2026-98101 (GCVE-0-2026-98101)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:35 – Updated: 2026-09-25 10:35
VLAI
Title
ipv6: mcast: use copy-on-write RCU updates in ip6_mc_source()
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: use copy-on-write RCU updates in ip6_mc_source() pmc->sflist is read locklessly under rcu_read_lock() by inet6_mc_check() during packet reception in the UDP and RAW multicast receive paths. ip6_mc_source() mutated psl->sl_addr and psl->sl_count in-place when adding or removing a source filter. Additionally, when expanding the filter buffer, newpsl was published via rcu_assign_pointer() before writing the new source into the array. Because 16-byte struct in6_addr writes are not atomic and array shifting is not synchronized with RCU readers, concurrent readers in inet6_mc_check() could read torn IPv6 addresses or observe duplicated/missed source entries. Fix this by switching ip6_mc_source() to copy-on-write RCU updates: allocate and fully populate newpsl before publishing it via rcu_assign_pointer(), and reclaim the old filter via kfree_rcu(), matching ip6_mc_msfilter(). Also remove the now unused IP6_SFBLOCK macro.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 882ba1f73c06831f2a21044ebd8864c485ac04f2 , < 2c2091e2ee93049fc513ad1e6c99d8b6c809f467 (git)
Affected: 882ba1f73c06831f2a21044ebd8864c485ac04f2 , < 20db91a052332ef5552bd2f651ffb9db911cf67b (git)
Affected: 882ba1f73c06831f2a21044ebd8864c485ac04f2 , < c073d1b070f171d206b19c98d71739a97f15b3f1 (git)
Affected: 47c75e3923c8d562fea8daf0ccf31546a7bef0ea (git)
Affected: 5.10.261 , < 5.11 (semver)
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Linux Linux Affected: 5.13
Unaffected: 0 , < 5.13 (semver)
Unaffected: 6.18.53 , ≤ 6.18.* (semver)
Unaffected: 7.2.7 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/net/if_inet6.h",
            "net/ipv6/mcast.c"
          ],
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          "vendor": "Linux",
          "versions": [
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              "versionType": "semver"
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              "versionType": "semver"
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              "status": "unaffected",
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              "versionType": "original_commit_for_fix"
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                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
            }
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: mcast: use copy-on-write RCU updates in ip6_mc_source()\n\npmc-\u003esflist is read locklessly under rcu_read_lock() by\ninet6_mc_check() during packet reception in the UDP and RAW\nmulticast receive paths.\n\nip6_mc_source() mutated psl-\u003esl_addr and psl-\u003esl_count in-place\nwhen adding or removing a source filter. Additionally, when expanding\nthe filter buffer, newpsl was published via rcu_assign_pointer()\nbefore writing the new source into the array.\n\nBecause 16-byte struct in6_addr writes are not atomic and array\nshifting is not synchronized with RCU readers, concurrent readers in\ninet6_mc_check() could read torn IPv6 addresses or observe\nduplicated/missed source entries.\n\nFix this by switching ip6_mc_source() to copy-on-write RCU updates:\nallocate and fully populate newpsl before publishing it via\nrcu_assign_pointer(), and reclaim the old filter via kfree_rcu(),\nmatching ip6_mc_msfilter().\n\nAlso remove the now unused IP6_SFBLOCK macro."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T10:35:52.731Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/2c2091e2ee93049fc513ad1e6c99d8b6c809f467"
        },
        {
          "url": "https://git.kernel.org/stable/c/20db91a052332ef5552bd2f651ffb9db911cf67b"
        },
        {
          "url": "https://git.kernel.org/stable/c/c073d1b070f171d206b19c98d71739a97f15b3f1"
        }
      ],
      "title": "ipv6: mcast: use copy-on-write RCU updates in ip6_mc_source()",
      "x_generator": {
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      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98101",
    "datePublished": "2026-09-25T10:35:52.731Z",
    "dateReserved": "2026-09-25T10:25:14.315Z",
    "dateUpdated": "2026-09-25T10:35:52.731Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
      "cve": {
        "affected": [
          {
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                "product": "Linux",
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                  "include/net/if_inet6.h",
                  "net/ipv6/mcast.c"
                ],
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                ],
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                "vendor": "Linux",
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            ],
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        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: mcast: use copy-on-write RCU updates in ip6_mc_source()\n\npmc-\u003esflist is read locklessly under rcu_read_lock() by\ninet6_mc_check() during packet reception in the UDP and RAW\nmulticast receive paths.\n\nip6_mc_source() mutated psl-\u003esl_addr and psl-\u003esl_count in-place\nwhen adding or removing a source filter. Additionally, when expanding\nthe filter buffer, newpsl was published via rcu_assign_pointer()\nbefore writing the new source into the array.\n\nBecause 16-byte struct in6_addr writes are not atomic and array\nshifting is not synchronized with RCU readers, concurrent readers in\ninet6_mc_check() could read torn IPv6 addresses or observe\nduplicated/missed source entries.\n\nFix this by switching ip6_mc_source() to copy-on-write RCU updates:\nallocate and fully populate newpsl before publishing it via\nrcu_assign_pointer(), and reclaim the old filter via kfree_rcu(),\nmatching ip6_mc_msfilter().\n\nAlso remove the now unused IP6_SFBLOCK macro."
          }
        ],
        "id": "CVE-2026-98101",
        "lastModified": "2026-09-25T11:17:39.830",
        "metrics": {},
        "published": "2026-09-25T11:17:39.830",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/20db91a052332ef5552bd2f651ffb9db911cf67b"
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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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.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.