{"id":"CVE-2026-23240","state":"PUBLISHED","title":"tls: Fix race condition in tls_sw_cancel_work_tx()","description":"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, &tx_ctx->tx_bitmask))\n    set_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask);\n    cancel_delayed_work_sync(&ctx->tx_work.work);\n                                     schedule_delayed_work(&tx_ctx->tx_work.work, 0);\n\nTo prevent this race condition, cancel_delayed_work_sync() is\nreplaced with disable_delayed_work_sync().","publishedAt":"2026-03-10T17:28:27.371Z","updatedAt":"2026-10-19T18:35:39.775Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4","status":"affected","lessThan":"a5de36d6cee74a92c1a21b260bc507e64bc451de","versionType":"git"},{"version":"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4","status":"affected","lessThan":"854cd32bc74fe573353095e90958490e4e4d641b","versionType":"git"},{"version":"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4","status":"affected","lessThan":"17153f154f80be2b47ebf52840f2d8f724eb2f3b","versionType":"git"},{"version":"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4","status":"affected","lessThan":"7bb09315f93dce6acc54bf59e5a95ba7365c2be4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/tls/tls_sw.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"6.12.75","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.16","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.6","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/tls/tls_sw.c"]}],"references":["https://git.kernel.org/stable/c/a5de36d6cee74a92c1a21b260bc507e64bc451de","https://git.kernel.org/stable/c/854cd32bc74fe573353095e90958490e4e4d641b","https://git.kernel.org/stable/c/17153f154f80be2b47ebf52840f2d8f724eb2f3b","https://git.kernel.org/stable/c/7bb09315f93dce6acc54bf59e5a95ba7365c2be4"],"weaknesses":["CWE-362"],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/23xxx/CVE-2026-23240.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23240","state":"PUBLISHED","datePublished":"2026-03-10T17:28:27.371Z","dateUpdated":"2026-10-19T18:35:39.775Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-01-13T15:37:45.989Z"},"containers":{"cna":{"title":"tls: Fix race condition in tls_sw_cancel_work_tx()","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, &tx_ctx->tx_bitmask))\n    set_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask);\n    cancel_delayed_work_sync(&ctx->tx_work.work);\n                                     schedule_delayed_work(&tx_ctx->tx_work.work, 0);\n\nTo prevent this race condition, cancel_delayed_work_sync() is\nreplaced with disable_delayed_work_sync()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4","status":"affected","lessThan":"a5de36d6cee74a92c1a21b260bc507e64bc451de","versionType":"git"},{"version":"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4","status":"affected","lessThan":"854cd32bc74fe573353095e90958490e4e4d641b","versionType":"git"},{"version":"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4","status":"affected","lessThan":"17153f154f80be2b47ebf52840f2d8f724eb2f3b","versionType":"git"},{"version":"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4","status":"affected","lessThan":"7bb09315f93dce6acc54bf59e5a95ba7365c2be4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/tls/tls_sw.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"6.12.75","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.16","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.6","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/tls/tls_sw.c"]}],"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"}],"metrics":[{"cvssV3_1":{"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"},"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 → tcp_check_space → tcp_new_space → sk->sk_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's 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":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:20:50.947Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"6.12.75"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"6.18.16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"6.19.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-23240","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:06:53.340021Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-362","lang":"en","type":"CWE","description":"CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T18:35:39.775Z"}}]}}}