CVE-2026-23240 (GCVE-0-2026-23240)
Vulnerability from cvelistv5 – Published: 2026-03-10 17:28 – Updated: 2026-08-05 12:20
VLAI
EPSS
VEX
Title
tls: Fix race condition in tls_sw_cancel_work_tx()
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().
Severity
9.8 (Critical)
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
f87e62d45e51b12d48d2cb46b5cde8f83b866bc4 , < a5de36d6cee74a92c1a21b260bc507e64bc451de
(git)
Affected: f87e62d45e51b12d48d2cb46b5cde8f83b866bc4 , < 854cd32bc74fe573353095e90958490e4e4d641b (git) Affected: f87e62d45e51b12d48d2cb46b5cde8f83b866bc4 , < 17153f154f80be2b47ebf52840f2d8f724eb2f3b (git) Affected: f87e62d45e51b12d48d2cb46b5cde8f83b866bc4 , < 7bb09315f93dce6acc54bf59e5a95ba7365c2be4 (git) |
guessed | |
| Linux | Linux |
Affected:
5.3
Unaffected: 0 , < 5.3 (semver) Unaffected: 6.12.75 , ≤ 6.12.* (semver) Unaffected: 6.18.16 , ≤ 6.18.* (semver) Unaffected: 6.19.6 , ≤ 6.19.* (semver) Unaffected: 7.0 , ≤ * (original_commit_for_fix) |
guessed |
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/tls/tls_sw.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "a5de36d6cee74a92c1a21b260bc507e64bc451de",
"status": "affected",
"version": "f87e62d45e51b12d48d2cb46b5cde8f83b866bc4",
"versionType": "git"
},
{
"lessThan": "854cd32bc74fe573353095e90958490e4e4d641b",
"status": "affected",
"version": "f87e62d45e51b12d48d2cb46b5cde8f83b866bc4",
"versionType": "git"
},
{
"lessThan": "17153f154f80be2b47ebf52840f2d8f724eb2f3b",
"status": "affected",
"version": "f87e62d45e51b12d48d2cb46b5cde8f83b866bc4",
"versionType": "git"
},
{
"lessThan": "7bb09315f93dce6acc54bf59e5a95ba7365c2be4",
"status": "affected",
"version": "f87e62d45e51b12d48d2cb46b5cde8f83b866bc4",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/tls/tls_sw.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.3"
},
{
"lessThan": "5.3",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.75",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.16",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.19.*",
"status": "unaffected",
"version": "6.19.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.75",
"versionStartIncluding": "5.3",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.16",
"versionStartIncluding": "5.3",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.19.6",
"versionStartIncluding": "5.3",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.0",
"versionStartIncluding": "5.3",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"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",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-23240",
"date": "2026-09-16",
"epss": "0.0049",
"percentile": "0.40967"
},
"microsoft_vex": {
"current_release_date": "2026-08-10T14:51:23.000Z",
"cve": "CVE-2026-23240",
"id": "msrc_CVE-2026-23240",
"initial_release_date": "2026-03-12T01:01:42.000Z",
"product_status:known_affected": "11",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "tls: Fix race condition in tls_sw_cancel_work_tx()",
"url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-23240.json",
"version": "12"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-23240\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-03-10T18:18:13.533\",\"lastModified\":\"2026-06-17T10:21:10.067\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"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().\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\\n\\ntls: Correcci\u00f3n de condici\u00f3n de carrera en tls_sw_cancel_work_tx()\\n\\nEste problema fue descubierto durante una auditor\u00eda de c\u00f3digo.\\n\\nDespu\u00e9s de que se llama a cancel_delayed_work_sync() desde tls_sk_proto_close(), tx_work_handler() a\u00fan puede ser programado desde rutas como el gestor de ACK Retrasado o ksoftirqd. Como resultado, el trabajador tx_work_handler() puede desreferenciar un objeto TLS liberado.\\n\\nEl siguiente es un escenario de condici\u00f3n de carrera simple:\\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, \u0026amp;tx_ctx-\u0026gt;tx_bitmask))\\n set_bit(BIT_TX_SCHEDULED, \u0026amp;ctx-\u0026gt;tx_bitmask);\\n cancel_delayed_work_sync(\u0026amp;ctx-\u0026gt;tx_work.work);\\n schedule_delayed_work(\u0026amp;tx_ctx-\u0026gt;tx_work.work, 0);\\n\\nPara prevenir esta condici\u00f3n de carrera, cancel_delayed_work_sync() es reemplazado por disable_delayed_work_sync().\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/tls/tls_sw.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4\",\"lessThan\":\"a5de36d6cee74a92c1a21b260bc507e64bc451de\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4\",\"lessThan\":\"854cd32bc74fe573353095e90958490e4e4d641b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4\",\"lessThan\":\"17153f154f80be2b47ebf52840f2d8f724eb2f3b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f87e62d45e51b12d48d2cb46b5cde8f83b866bc4\",\"lessThan\":\"7bb09315f93dce6acc54bf59e5a95ba7365c2be4\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/tls/tls_sw.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.3\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.3\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.75\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.16\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.19.6\",\"lessThanOrEqual\":\"6.19.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0\",\"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}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-362\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.3.1\",\"versionEndExcluding\":\"6.12.75\",\"matchCriteriaId\":\"2CD7FB69-6705-47EA-9F0D-65B1E859F71E\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.13\",\"versionEndExcluding\":\"6.18.16\",\"matchCriteriaId\":\"B4B8CDA9-BADF-4CF5-8B3B-702DE8EEA40B\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.19\",\"versionEndExcluding\":\"6.19.6\",\"matchCriteriaId\":\"373EEEDA-FAA1-4FB4-B6ED-DB4DD99DBE67\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:5.3:-:*:*:*:*:*:*\",\"matchCriteriaId\":\"D036D76E-AC69-4382-B4C1-8EDA1ABB2941\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:5.3:rc4:*:*:*:*:*:*\",\"matchCriteriaId\":\"EBAE804E-3CC3-44C2-B1F5-2DC3EE4FF793\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:5.3:rc5:*:*:*:*:*:*\",\"matchCriteriaId\":\"8721379D-C6BC-43BF-8098-396F32182BEF\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:5.3:rc6:*:*:*:*:*:*\",\"matchCriteriaId\":\"65AF2469-2B9F-4D4D-8886-2B8BA66D5FDC\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:5.3:rc7:*:*:*:*:*:*\",\"matchCriteriaId\":\"21001886-2C34-45F4-9319-60102B357E64\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:5.3:rc8:*:*:*:*:*:*\",\"matchCriteriaId\":\"999345BA-F820-40B9-A711-32CA9265C289\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*\",\"matchCriteriaId\":\"F253B622-8837-4245-BCE5-A7BF8FC76A16\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/17153f154f80be2b47ebf52840f2d8f724eb2f3b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/7bb09315f93dce6acc54bf59e5a95ba7365c2be4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/854cd32bc74fe573353095e90958490e4e4d641b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/a5de36d6cee74a92c1a21b260bc507e64bc451de\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}",
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-07-02T17:12:11+00:00",
"cve": "CVE-2026-23240",
"id": "CVE-2026-23240",
"initial_release_date": "2026-03-10T00:00:00+00:00",
"product_status:known_affected": "230",
"product_status:known_not_affected": "44",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: Linux kernel: Denial of service due to a race condition in the TLS subsystem",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23240.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "important",
"current_release_date": "2026-09-11T01:37:41Z",
"cve": "CVE-2026-23240",
"id": "CVE-2026-23240",
"initial_release_date": "2026-03-11T00:27:35Z",
"product_status:first_fixed": "2",
"product_status:known_affected": "453",
"product_status:known_not_affected": "153",
"product_status:recommended": "619",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-23240",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-23240.json",
"version": "50"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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.
Sightings
| Author | Source | Type | Date | Other |
|---|
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.
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
Loading…