CVE-2026-98101 (GCVE-0-2026-98101)
Vulnerability from cvelistv5
Published
2026-09-25 10:35
Modified
2026-10-19 09:13
Severity ?
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: 882ba1f73c06831f2a21044ebd8864c485ac04f2
Version: 882ba1f73c06831f2a21044ebd8864c485ac04f2
Version: 882ba1f73c06831f2a21044ebd8864c485ac04f2
Version: 882ba1f73c06831f2a21044ebd8864c485ac04f2
Version: 882ba1f73c06831f2a21044ebd8864c485ac04f2
Version: 47c75e3923c8d562fea8daf0ccf31546a7bef0ea
Version: 5.10.261   ≤
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{
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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": "2026-10-19T09:13:53.770Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/ac51321d3b2391860a935820ebcf4d8b9bb16a8a"
        },
        {
          "url": "https://git.kernel.org/stable/c/dba00514bf668c26cb4900e9f0da84bf96bf065a"
        },
        {
          "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()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98101",
    "datePublished": "2026-09-25T10:35:52.731Z",
    "dateReserved": "2026-09-25T10:25:14.315Z",
    "dateUpdated": "2026-10-19T09:13:53.770Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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