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CVE-2026-89536 (GCVE-0-2026-89536)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:44 – Updated: 2026-09-14 12:00
VLAI
Title
SUNRPC: wait for in-flight client TLS handshake callback
Summary
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: wait for in-flight client TLS handshake callback xs_tls_handshake_sync() gives xs_tls_handshake_done() a reference to the lower transport before submitting the handshake request. On timeout or signal, the synchronous waiter drops that reference after calling tls_handshake_cancel(). handshake_req_cancel() returns false when handshake_complete() has already marked the request complete. In that case the completion callback can still be running, so dropping the callback-owned reference in the waiter can free the lower transport before xs_tls_handshake_done() stores xprt_err or drops its own reference. If cancellation loses to completion, wait until xs_tls_handshake_done() signals handshake_done and let the callback release its reference. This mirrors the server-side handshake lifetime handling and keeps the timeout or signal return value unchanged.
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: 75eb6af7acdf566c68d61e98e67ee2f235201c02 , < fb43997407bc17ee39bac81ab708101312e255f5 (git)
Affected: 75eb6af7acdf566c68d61e98e67ee2f235201c02 , < 15431820f448e09f8029b670d5c82aa5917d4625 (git)
Affected: 75eb6af7acdf566c68d61e98e67ee2f235201c02 , < 1de391e8b94e31b45c19c16dbf315e294810c7de (git)
Affected: 75eb6af7acdf566c68d61e98e67ee2f235201c02 , < 7fbb6d2ab0391eb8d1f1a68e6bc263ef02cea61b (git)
Affected: 75eb6af7acdf566c68d61e98e67ee2f235201c02 , < a89dd597458848b463d284b15e42a8078beeb046 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.5
Unaffected: 0 , < 6.5 (semver)
Unaffected: 6.6.157 , ≤ 6.6.* (semver)
Unaffected: 6.12.109 , ≤ 6.12.* (semver)
Unaffected: 6.18.50 , ≤ 6.18.* (semver)
Unaffected: 7.2.4 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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Show details on NVD website
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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sunrpc/xprtsock.c"
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          "product": "Linux",
          "programFiles": [
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "6.5"
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            {
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              "status": "unaffected",
              "version": "0",
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            },
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              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.157",
                  "versionStartIncluding": "6.5",
                  "vulnerable": true
                },
                {
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                  "versionStartIncluding": "6.5",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: wait for in-flight client TLS handshake callback\n\nxs_tls_handshake_sync() gives xs_tls_handshake_done() a reference to the\nlower transport before submitting the handshake request. On timeout or\nsignal, the synchronous waiter drops that reference after calling\ntls_handshake_cancel().\n\nhandshake_req_cancel() returns false when handshake_complete() has\nalready marked the request complete. In that case the completion callback\ncan still be running, so dropping the callback-owned reference in the\nwaiter can free the lower transport before xs_tls_handshake_done() stores\nxprt_err or drops its own reference.\n\nIf cancellation loses to completion, wait until xs_tls_handshake_done()\nsignals handshake_done and let the callback release its reference. This\nmirrors the server-side handshake lifetime handling and keeps the timeout\nor signal return value unchanged."
        }
      ],
      "metrics": [
        {
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            "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"
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              "lang": "en",
              "value": "AV:N - The bug is in the SUNRPC TCP-with-TLS client handshake (xs_tls_handshake_sync), reached when a remote NFS/RPC peer completes RPC-with-TLS; a malicious server or on-path attacker with xprtsec=tls (anonymous TLS) drives handshake_complete() over the network against the client\u0027s 10s wait.\nAC:L - The attacker times TLS completion against the fixed XS_TLS_HANDSHAKE_TO window and can force repeated reconnects so tls_handshake_cancel() losing to handshake_complete() is reliably hittable, with no memory-layout guess or other condition outside attacker control.\nPR:N - No privileges on the victim host are required; a remote TLS peer only needs the client to initiate or re-establish an RPC-with-TLS connection, and the handshake runs after AUTH_TLS STARTTLS but before NFS credentials are verified.\nUI:N - No victim action is needed at attack time once an NFS xprtsec=tls/mtls mount exists, because idle disconnect or server-induced reconnect automatically re-enters xs_tcp_tls_setup_socket() and the handshake wait.\nS:U - The use-after-free corrupts kernel heap state in the SUNRPC client on the same host; impact stays within that kernel\u0027s security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - When cancel loses, the waiter still xprt_put()s the callback-owned rpc_xprt reference, so sock_xprt can be freed while xs_tls_handshake_done() writes xprt_err and the connect worker still uses lower_xprt, a heap UAF enabling arbitrary disclosure.\nI:H - Use-after-free of rpc_xprt/sock_xprt (ops pointers, wait queues, socket state) allows heap reuse for arbitrary writes and control-flow hijacking, not merely a crash.\nA:H - The extra put can destroy the transport while the handshake waiter and connect worker still touch it, producing a kernel oops/panic or a hang in xprt_destroy waiting on XPRT_LOCKED, denying NFS/RPC service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-14T12:00:45.076Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/fb43997407bc17ee39bac81ab708101312e255f5"
        },
        {
          "url": "https://git.kernel.org/stable/c/15431820f448e09f8029b670d5c82aa5917d4625"
        },
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        },
        {
          "url": "https://git.kernel.org/stable/c/a89dd597458848b463d284b15e42a8078beeb046"
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      "title": "SUNRPC: wait for in-flight client TLS handshake callback",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89536",
    "datePublished": "2026-09-11T19:44:14.473Z",
    "dateReserved": "2026-09-11T19:38:34.721Z",
    "dateUpdated": "2026-09-14T12:00:45.076Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-09-17",
      "epss": "0.00626",
      "percentile": "0.48434"
    },
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-13T06:57:07+00:00",
      "cve": "CVE-2026-89536",
      "id": "CVE-2026-89536",
      "initial_release_date": "2026-09-11T19:44:14.473000+00:00",
      "product_status:known_affected": "2",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel: Memory corruption in SUNRPC client TLS handshake",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89536.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-16T15:37:14Z",
      "cve": "CVE-2026-89536",
      "id": "CVE-2026-89536",
      "initial_release_date": "2026-09-12T16:26:33Z",
      "product_status:known_affected": "114",
      "product_status:known_not_affected": "239",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89536",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89536.json",
      "version": "4"
    }
  }
}



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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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • 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.


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