CVE-2026-63978 (GCVE-0-2026-63978)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:56 – Updated: 2026-07-20 13:42
VLAI
Title
net/handshake: Drain pending requests at net namespace exit
Summary
In the Linux kernel, the following vulnerability has been resolved: net/handshake: Drain pending requests at net namespace exit The arguments to list_splice_init() in handshake_net_exit() are reversed. The call moves the local empty "requests" list onto hn->hn_requests, leaving the local list empty, so the subsequent drain loop runs zero iterations. Pending handshake requests that had not yet been accepted are not torn down when the net namespace is destroyed; each one keeps a reference on a socket file and on the handshake_req allocation. Pass the source and destination in the documented order (list_splice_init(list, head) moves list onto head) so the pending list is transferred to the local scratch list and drained through handshake_complete(). Fixing the splice direction exposes a list-corruption race. After the splice each req->hr_list still has non-empty link pointers, threading the stack-local scratch list rather than hn_requests. A concurrent handshake_req_cancel() -- for example, from sunrpc's TLS timeout on a kernel socket whose netns reference was not taken -- finds the request through the rhashtable, calls remove_pending(), and sees !list_empty(&req->hr_list). __remove_pending_locked() then list_del_init()s an entry off the scratch list while the drain iterates, corrupting it. The same call arriving after the drain loop has run list_del() on an entry hits LIST_POISON instead. Have remove_pending() check HANDSHAKE_F_NET_DRAINING under hn_lock and report not-found when drain is in progress. The drain has already taken ownership; handshake_complete()'s existing test_and_set on HANDSHAKE_F_REQ_COMPLETED still arbitrates between drain and cancel for who calls the consumer's hp_done. Use list_del_init() rather than list_del() in the drain so req->hr_list does not carry LIST_POISON after drain releases the entry. The DRAINING guard in remove_pending() makes cancel return false, but cancel still falls through to test_and_set_bit on HANDSHAKE_F_REQ_COMPLETED and drops the request's hr_file reference. Without another pin, if that is the last reference, sk_destruct frees the request while it is still linked on the drain loop's local list. Pin each request's hr_file under hn_lock before releasing the list, and drop that drain pin after the loop finishes with the request.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 3b3009ea8abb713b022d94fba95ec270cf6e7eae , < 9ec20c9a5a04f2c3f1cf65d21f886d7aaa6189cd (git)
Affected: 3b3009ea8abb713b022d94fba95ec270cf6e7eae , < 8c35539db0ab0bfa1ea44efab00b053261a69469 (git)
Affected: 3b3009ea8abb713b022d94fba95ec270cf6e7eae , < ea5fe6a73ca57e5150b8a38b341aef2636eb72f0 (git)
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Linux Linux Affected: 6.4
Unaffected: 0 , < 6.4 (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/handshake/netlink.c",
            "net/handshake/request.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "9ec20c9a5a04f2c3f1cf65d21f886d7aaa6189cd",
              "status": "affected",
              "version": "3b3009ea8abb713b022d94fba95ec270cf6e7eae",
              "versionType": "git"
            },
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              "status": "affected",
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              "versionType": "git"
            },
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              "status": "affected",
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              "versionType": "git"
            }
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          "product": "Linux",
          "programFiles": [
            "net/handshake/netlink.c",
            "net/handshake/request.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.4"
            },
            {
              "lessThan": "6.4",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.93",
                  "versionStartIncluding": "6.4",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.12",
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              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/handshake: Drain pending requests at net namespace exit\n\nThe arguments to list_splice_init() in handshake_net_exit() are\nreversed. The call moves the local empty \"requests\" list onto\nhn-\u003ehn_requests, leaving the local list empty, so the subsequent\ndrain loop runs zero iterations. Pending handshake requests that\nhad not yet been accepted are not torn down when the net namespace\nis destroyed; each one keeps a reference on a socket file and on\nthe handshake_req allocation.\n\nPass the source and destination in the documented order\n(list_splice_init(list, head) moves list onto head) so the pending\nlist is transferred to the local scratch list and drained through\nhandshake_complete().\n\nFixing the splice direction exposes a list-corruption race. After\nthe splice each req-\u003ehr_list still has non-empty link pointers,\nthreading the stack-local scratch list rather than hn_requests.\nA concurrent handshake_req_cancel() -- for example, from sunrpc\u0027s\nTLS timeout on a kernel socket whose netns reference was not\ntaken -- finds the request through the rhashtable, calls\nremove_pending(), and sees !list_empty(\u0026req-\u003ehr_list).\n__remove_pending_locked() then list_del_init()s an entry off the\nscratch list while the drain iterates, corrupting it. The same\ncall arriving after the drain loop has run list_del() on an\nentry hits LIST_POISON instead.\n\nHave remove_pending() check HANDSHAKE_F_NET_DRAINING under\nhn_lock and report not-found when drain is in progress. The\ndrain has already taken ownership; handshake_complete()\u0027s existing\ntest_and_set on HANDSHAKE_F_REQ_COMPLETED still arbitrates\nbetween drain and cancel for who calls the consumer\u0027s hp_done. Use\nlist_del_init() rather than list_del() in the drain so req-\u003ehr_list\ndoes not carry LIST_POISON after drain releases the entry.\n\nThe DRAINING guard in remove_pending() makes cancel return false,\nbut cancel still falls through to test_and_set_bit on\nHANDSHAKE_F_REQ_COMPLETED and drops the request\u0027s hr_file reference.\nWithout another pin, if that is the last reference, sk_destruct frees\nthe request while it is still linked on the drain loop\u0027s local list.\nPin each request\u0027s hr_file under hn_lock before releasing the list,\nand drop that drain pin after the loop finishes with the request."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-20T13:42:02.047Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/9ec20c9a5a04f2c3f1cf65d21f886d7aaa6189cd"
        },
        {
          "url": "https://git.kernel.org/stable/c/8c35539db0ab0bfa1ea44efab00b053261a69469"
        },
        {
          "url": "https://git.kernel.org/stable/c/ea5fe6a73ca57e5150b8a38b341aef2636eb72f0"
        }
      ],
      "title": "net/handshake: Drain pending requests at net namespace exit",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63978",
    "datePublished": "2026-07-19T14:56:02.484Z",
    "dateReserved": "2026-07-19T07:54:57.025Z",
    "dateUpdated": "2026-07-20T13:42:02.047Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-63978",
      "date": "2026-07-21",
      "epss": "0.00605",
      "percentile": "0.45094"
    },
    "microsoft_vex": {
      "current_release_date": "2026-07-21T01:04:58.000Z",
      "cve": "CVE-2026-63978",
      "id": "msrc_CVE-2026-63978",
      "initial_release_date": "2026-07-21T01:04:58.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "net/handshake: Drain pending requests at net namespace exit",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63978.json",
      "version": "1"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-63978\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-07-19T16:17:16.957\",\"lastModified\":\"2026-07-20T15:17:00.063\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet/handshake: Drain pending requests at net namespace exit\\n\\nThe arguments to list_splice_init() in handshake_net_exit() are\\nreversed. The call moves the local empty \\\"requests\\\" list onto\\nhn-\u003ehn_requests, leaving the local list empty, so the subsequent\\ndrain loop runs zero iterations. Pending handshake requests that\\nhad not yet been accepted are not torn down when the net namespace\\nis destroyed; each one keeps a reference on a socket file and on\\nthe handshake_req allocation.\\n\\nPass the source and destination in the documented order\\n(list_splice_init(list, head) moves list onto head) so the pending\\nlist is transferred to the local scratch list and drained through\\nhandshake_complete().\\n\\nFixing the splice direction exposes a list-corruption race. After\\nthe splice each req-\u003ehr_list still has non-empty link pointers,\\nthreading the stack-local scratch list rather than hn_requests.\\nA concurrent handshake_req_cancel() -- for example, from sunrpc\u0027s\\nTLS timeout on a kernel socket whose netns reference was not\\ntaken -- finds the request through the rhashtable, calls\\nremove_pending(), and sees !list_empty(\u0026req-\u003ehr_list).\\n__remove_pending_locked() then list_del_init()s an entry off the\\nscratch list while the drain iterates, corrupting it. The same\\ncall arriving after the drain loop has run list_del() on an\\nentry hits LIST_POISON instead.\\n\\nHave remove_pending() check HANDSHAKE_F_NET_DRAINING under\\nhn_lock and report not-found when drain is in progress. The\\ndrain has already taken ownership; handshake_complete()\u0027s existing\\ntest_and_set on HANDSHAKE_F_REQ_COMPLETED still arbitrates\\nbetween drain and cancel for who calls the consumer\u0027s hp_done. Use\\nlist_del_init() rather than list_del() in the drain so req-\u003ehr_list\\ndoes not carry LIST_POISON after drain releases the entry.\\n\\nThe DRAINING guard in remove_pending() makes cancel return false,\\nbut cancel still falls through to test_and_set_bit on\\nHANDSHAKE_F_REQ_COMPLETED and drops the request\u0027s hr_file reference.\\nWithout another pin, if that is the last reference, sk_destruct frees\\nthe request while it is still linked on the drain loop\u0027s local list.\\nPin each request\u0027s hr_file under hn_lock before releasing the list,\\nand drop that drain pin after the loop finishes with the request.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/handshake/netlink.c\",\"net/handshake/request.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"3b3009ea8abb713b022d94fba95ec270cf6e7eae\",\"lessThan\":\"9ec20c9a5a04f2c3f1cf65d21f886d7aaa6189cd\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"3b3009ea8abb713b022d94fba95ec270cf6e7eae\",\"lessThan\":\"8c35539db0ab0bfa1ea44efab00b053261a69469\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"3b3009ea8abb713b022d94fba95ec270cf6e7eae\",\"lessThan\":\"ea5fe6a73ca57e5150b8a38b341aef2636eb72f0\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/handshake/netlink.c\",\"net/handshake/request.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.4\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.4\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.93\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0.12\",\"lessThanOrEqual\":\"7.0.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/8c35539db0ab0bfa1ea44efab00b053261a69469\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9ec20c9a5a04f2c3f1cf65d21f886d7aaa6189cd\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ea5fe6a73ca57e5150b8a38b341aef2636eb72f0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}



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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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  • 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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  • 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.


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