CVE-2025-68775 (GCVE-0-2025-68775)

Vulnerability from cvelistv5 – Published: 2026-01-13 15:28 – Updated: 2026-08-05 12:11
VLAI
Title
net/handshake: duplicate handshake cancellations leak socket
Summary
In the Linux kernel, the following vulnerability has been resolved: net/handshake: duplicate handshake cancellations leak socket When a handshake request is cancelled it is removed from the handshake_net->hn_requests list, but it is still present in the handshake_rhashtbl until it is destroyed. If a second cancellation request arrives for the same handshake request, then remove_pending() will return false... and assuming HANDSHAKE_F_REQ_COMPLETED isn't set in req->hr_flags, we'll continue processing through the out_true label, where we put another reference on the sock and a refcount underflow occurs. This can happen for example if a handshake times out - particularly if the SUNRPC client sends the AUTH_TLS probe to the server but doesn't follow it up with the ClientHello due to a problem with tlshd. When the timeout is hit on the server, the server will send a FIN, which triggers a cancellation request via xs_reset_transport(). When the timeout is hit on the client, another cancellation request happens via xs_tls_handshake_sync(). Add a test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED) in the pending cancel path so duplicate cancels can be detected.
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 CPE status
Linux Linux Affected: 3b3009ea8abb713b022d94fba95ec270cf6e7eae , < 011ae80c49d9bfa5b4336f8bd387cd25c7593663 (git)
Affected: 3b3009ea8abb713b022d94fba95ec270cf6e7eae , < e1641177e7fb48a0a5a06658d4aab51da6656659 (git)
Affected: 3b3009ea8abb713b022d94fba95ec270cf6e7eae , < 3c330f1dee3cd92b57e19b9d21dc8ce5970b09be (git)
Affected: 3b3009ea8abb713b022d94fba95ec270cf6e7eae , < 15564bd67e2975002f2a8e9defee33e321d3183f (git)
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Linux Linux Affected: 6.4
Unaffected: 0 , < 6.4 (semver)
Unaffected: 6.6.120 , ≤ 6.6.* (semver)
Unaffected: 6.12.64 , ≤ 6.12.* (semver)
Unaffected: 6.18.3 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
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          "product": "Linux",
          "programFiles": [
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          "vendor": "Linux",
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              "versionType": "semver"
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              "version": "6.18.3",
              "versionType": "semver"
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              "status": "unaffected",
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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                  "versionEndExcluding": "6.12.64",
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                  "vulnerable": true
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                  "versionEndExcluding": "6.18.3",
                  "versionStartIncluding": "6.4",
                  "vulnerable": true
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                  "versionEndExcluding": "6.19",
                  "versionStartIncluding": "6.4",
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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\nnet/handshake: duplicate handshake cancellations leak socket\n\nWhen a handshake request is cancelled it is removed from the\nhandshake_net-\u003ehn_requests list, but it is still present in the\nhandshake_rhashtbl until it is destroyed.\n\nIf a second cancellation request arrives for the same handshake request,\nthen remove_pending() will return false... and assuming\nHANDSHAKE_F_REQ_COMPLETED isn\u0027t set in req-\u003ehr_flags, we\u0027ll continue\nprocessing through the out_true label, where we put another reference on\nthe sock and a refcount underflow occurs.\n\nThis can happen for example if a handshake times out - particularly if\nthe SUNRPC client sends the AUTH_TLS probe to the server but doesn\u0027t\nfollow it up with the ClientHello due to a problem with tlshd.  When the\ntimeout is hit on the server, the server will send a FIN, which triggers\na cancellation request via xs_reset_transport().  When the timeout is\nhit on the client, another cancellation request happens via\nxs_tls_handshake_sync().\n\nAdd a test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED) in the pending cancel\npath so duplicate cancels can be detected."
        }
      ],
      "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"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - An unauthenticated remote client can reach the bug through a network-facing SUNRPC/NFS server by sending an AUTH_TLS NULL probe. TCP receive processing reaches svcauth_tls_accept(), svc_tcp_handshake(), and ultimately duplicate handshake cancellation.\nAC:L - The attacker can create and abandon concurrent AUTH_TLS connections to keep requests pending and drive both timeout and transport-teardown cancellations. No memory-layout guess or uncontrollable race is required.\nPR:N - AUTH_TLS is processed before RPC credentials are authenticated, and the probe requires no established identity, account, or kernel capability.\nUI:N - The server processes the probe, timeout, and socket teardown automatically without victim user action.\nS:U - Exploitation affects the same host-kernel security authority processing the request and does not cross a VM, IOMMU, or comparable security boundary.\nC:H - The extra sock_put() can prematurely free a still-referenced socket, producing a reclaimable kernel use-after-free capable of exposing arbitrary kernel memory.\nI:H - Reclaiming the prematurely freed socket object can provide attacker-controlled data to subsequent kernel accesses, enabling arbitrary modification or control-flow hijacking.\nA:H - The socket use-after-free can cause a kernel oops or panic, while repeated unauthenticated triggers can also leak sockets and exhaust resources."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:11:25.376Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/011ae80c49d9bfa5b4336f8bd387cd25c7593663"
        },
        {
          "url": "https://git.kernel.org/stable/c/e1641177e7fb48a0a5a06658d4aab51da6656659"
        },
        {
          "url": "https://git.kernel.org/stable/c/3c330f1dee3cd92b57e19b9d21dc8ce5970b09be"
        },
        {
          "url": "https://git.kernel.org/stable/c/15564bd67e2975002f2a8e9defee33e321d3183f"
        }
      ],
      "title": "net/handshake: duplicate handshake cancellations leak socket",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-68775",
    "datePublished": "2026-01-13T15:28:52.069Z",
    "dateReserved": "2025-12-24T10:30:51.035Z",
    "dateUpdated": "2026-08-05T12:11:25.376Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "date": "2026-09-21",
      "epss": "0.00535",
      "percentile": "0.43907"
    },
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                "product": "Linux",
                "programFiles": [
                  "net/handshake/request.c"
                ],
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                "vendor": "Linux",
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                "vendor": "Linux",
                "versions": [
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                    "status": "affected",
                    "version": "6.4"
                  },
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                    "status": "unaffected",
                    "version": "0",
                    "versionType": "semver"
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                    "versionType": "semver"
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                    "versionType": "semver"
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                    "status": "unaffected",
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                    "status": "unaffected",
                    "version": "6.19",
                    "versionType": "original_commit_for_fix"
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/handshake: duplicate handshake cancellations leak socket\n\nWhen a handshake request is cancelled it is removed from the\nhandshake_net-\u003ehn_requests list, but it is still present in the\nhandshake_rhashtbl until it is destroyed.\n\nIf a second cancellation request arrives for the same handshake request,\nthen remove_pending() will return false... and assuming\nHANDSHAKE_F_REQ_COMPLETED isn\u0027t set in req-\u003ehr_flags, we\u0027ll continue\nprocessing through the out_true label, where we put another reference on\nthe sock and a refcount underflow occurs.\n\nThis can happen for example if a handshake times out - particularly if\nthe SUNRPC client sends the AUTH_TLS probe to the server but doesn\u0027t\nfollow it up with the ClientHello due to a problem with tlshd.  When the\ntimeout is hit on the server, the server will send a FIN, which triggers\na cancellation request via xs_reset_transport().  When the timeout is\nhit on the client, another cancellation request happens via\nxs_tls_handshake_sync().\n\nAdd a test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED) in the pending cancel\npath so duplicate cancels can be detected."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnet/handshake: las cancelaciones duplicadas de handshake fugan el socket\n\nCuando una solicitud de handshake es cancelada, es eliminada de la lista handshake_net-\u0026gt;hn_requests, pero a\u00fan est\u00e1 presente en la handshake_rhashtbl hasta que es destruida.\n\nSi llega una segunda solicitud de cancelaci\u00f3n para la misma solicitud de handshake, entonces remove_pending() devolver\u00e1 falso... y asumiendo que HANDSHAKE_F_REQ_COMPLETED no est\u00e1 establecido en req-\u0026gt;hr_flags, continuaremos procesando a trav\u00e9s de la etiqueta out_true, donde ponemos otra referencia en el sock y ocurre un desbordamiento negativo del contador de referencias.\n\nEsto puede ocurrir por ejemplo si un handshake agota el tiempo de espera, particularmente si el cliente SUNRPC env\u00eda la sonda AUTH_TLS al servidor pero no la sigue con el ClientHello debido a un problema con tlshd. Cuando se alcanza el tiempo de espera en el servidor, el servidor enviar\u00e1 un FIN, lo que activa una solicitud de cancelaci\u00f3n a trav\u00e9s de xs_reset_transport(). Cuando se alcanza el tiempo de espera en el cliente, ocurre otra solicitud de cancelaci\u00f3n a trav\u00e9s de xs_tls_handshake_sync().\n\nA\u00f1adir un test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED) en la ruta de cancelaci\u00f3n pendiente para que las cancelaciones duplicadas puedan ser detectadas."
          }
        ],
        "id": "CVE-2025-68775",
        "lastModified": "2026-07-30T06:24:43.687",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 9.8,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-01-13T16:15:57.073",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/011ae80c49d9bfa5b4336f8bd387cd25c7593663"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Deferred"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-08-21T20:46:50+00:00",
      "cve": "CVE-2025-68775",
      "id": "CVE-2025-68775",
      "initial_release_date": "2025-01-01T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net/handshake: duplicate handshake cancellations leak socket",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-68775.json",
      "version": "3"
    }
  }
}



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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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