CVE-2026-23240 (GCVE-0-2026-23240)
Vulnerability from cvelistv5
Published
2026-03-10 17:28
Modified
2026-08-05 12:20
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: tls: Fix race condition in tls_sw_cancel_work_tx() This issue was discovered during a code audit. After cancel_delayed_work_sync() is called from tls_sk_proto_close(), tx_work_handler() can still be scheduled from paths such as the Delayed ACK handler or ksoftirqd. As a result, the tx_work_handler() worker may dereference a freed TLS object. The following is a simple race scenario: cpu0 cpu1 tls_sk_proto_close() tls_sw_cancel_work_tx() tls_write_space() tls_sw_write_space() if (!test_and_set_bit(BIT_TX_SCHEDULED, &tx_ctx->tx_bitmask)) set_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask); cancel_delayed_work_sync(&ctx->tx_work.work); schedule_delayed_work(&tx_ctx->tx_work.work, 0); To prevent this race condition, cancel_delayed_work_sync() is replaced with disable_delayed_work_sync().
References
Impacted products
Vendor Product Version
Linux Linux Version: f87e62d45e51b12d48d2cb46b5cde8f83b866bc4
Version: f87e62d45e51b12d48d2cb46b5cde8f83b866bc4
Version: f87e62d45e51b12d48d2cb46b5cde8f83b866bc4
Version: f87e62d45e51b12d48d2cb46b5cde8f83b866bc4
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{
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          "programFiles": [
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              "version": "0",
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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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\ntls: Fix race condition in tls_sw_cancel_work_tx()\n\nThis issue was discovered during a code audit.\n\nAfter cancel_delayed_work_sync() is called from tls_sk_proto_close(),\ntx_work_handler() can still be scheduled from paths such as the\nDelayed ACK handler or ksoftirqd.\nAs a result, the tx_work_handler() worker may dereference a freed\nTLS object.\n\nThe following is a simple race scenario:\n\n          cpu0                         cpu1\n\ntls_sk_proto_close()\n  tls_sw_cancel_work_tx()\n                                 tls_write_space()\n                                   tls_sw_write_space()\n                                     if (!test_and_set_bit(BIT_TX_SCHEDULED, \u0026tx_ctx-\u003etx_bitmask))\n    set_bit(BIT_TX_SCHEDULED, \u0026ctx-\u003etx_bitmask);\n    cancel_delayed_work_sync(\u0026ctx-\u003etx_work.work);\n                                     schedule_delayed_work(\u0026tx_ctx-\u003etx_work.work, 0);\n\nTo prevent this race condition, cancel_delayed_work_sync() is\nreplaced with disable_delayed_work_sync()."
        }
      ],
      "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 - The tls_write_space callback is triggered by a remote TCP peer sending ACKs, which causes tcp_data_snd_check \u2192 tcp_check_space \u2192 tcp_new_space \u2192 sk-\u003esk_write_space (tls_write_space). Any server using kTLS (nginx, HAProxy, NFS with TLS) is reachable over the network.\nAC:L - The attacker controls both sides of the race: they send TCP ACKs to trigger tls_write_space and initiate disconnect to trigger the close path. With repeated connection attempts and ACK flooding, the race window is reliably winnable.\nPR:N - No authentication or privileges are needed to establish a TCP connection and send ACKs to a kTLS-enabled server. The race is triggered during normal TCP processing before any application-level authentication occurs.\nUI:N - No user interaction is needed. The attacker connects to the server, sends ACKs, and disconnects to trigger the race. The server processes this automatically.\nS:U - The vulnerability results in kernel-level use-after-free within the same security authority (kernel space). There is no crossing of a virtualization or sandbox boundary.\nC:H - This is a use-after-free where the freed tls_sw_context_tx (freed via immediate kfree, not kfree_rcu) can be reallocated with attacker-influenced data. The UAF gives read access to reallocated memory contents, enabling arbitrary kernel memory disclosure.\nI:H - The UAF on the tls_sw_context_tx structure enables heap spraying to control the freed object\u0027s contents. The tx_work_handler then calls tls_tx_records through corrupted context pointers, enabling control flow hijacking and arbitrary code execution.\nA:H - The use-after-free on the embedded delayed_work struct causes kernel crashes when the workqueue attempts to execute the freed work item, resulting in kernel panic or oops."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:20:50.947Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a5de36d6cee74a92c1a21b260bc507e64bc451de"
        },
        {
          "url": "https://git.kernel.org/stable/c/854cd32bc74fe573353095e90958490e4e4d641b"
        },
        {
          "url": "https://git.kernel.org/stable/c/17153f154f80be2b47ebf52840f2d8f724eb2f3b"
        },
        {
          "url": "https://git.kernel.org/stable/c/7bb09315f93dce6acc54bf59e5a95ba7365c2be4"
        }
      ],
      "title": "tls: Fix race condition in tls_sw_cancel_work_tx()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-23240",
    "datePublished": "2026-03-10T17:28:27.371Z",
    "dateReserved": "2026-01-13T15:37:45.989Z",
    "dateUpdated": "2026-08-05T12:20:50.947Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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