CVE-2026-74691
In the Linux kernel, the following vulnerability has been resolved:
net: thunderbolt: Tear down DMA paths before stopping the rings
tbnet_tear_down() stops both rings and frees their frame buffers before calling tb_xdomain_disable_paths(). tb_ring_stop() zeroes the ring's descriptor base and tbnet_free_buffers() unmaps and frees the pages the frames sit in, so by the time __tb_path_deactivate_hop() polls the hop's 'pending' bit, anything still in flight has nowhere to drain to.
The teardown sequence has been in this order since the driver was added. The setup path has not: commit ff7cd07f3064 ("net: thunderbolt: Enable DMA paths only after rings are enabled") moved the path enable to the end of tbnet_connected_work() and documented why:
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/* Both logins successful so enable the rings, high-speed DMA * paths and start the network device queue. * * Note we enable the DMA paths last to make sure we have primed * the Rx ring before any incoming packets are allowed to * arrive. */
Teardown was never updated to match, so the rings and the paths now come down in the same order they go up instead of in reverse.
On an ASMedia ASM4242 host router the 'pending' bit then never clears: every teardown burns the full 500 ms timeout and __tb_path_deactivate_hop() returns -ETIMEDOUT. Raising the timeout to 5 s does not help, so the hop is not slow to drain, it never drains at all.
The failure is invisible above the thunderbolt core. __tb_path_deactivate_hops() is void and only calls tb_port_warn(); tb_path_deactivate(), tb_tunnel_deactivate() and __tb_disconnect_xdomain_paths() are void as well, and tb_disconnect_xdomain_paths() ends in an unconditional "return 0". So tb_xdomain_disable_paths() reports success and the netdev_warn() below it never fires. Repeated teardowns eventually take the XDomain control channel down, after which the peer node is gone and only a power cycle brings the controller back.
Deactivating the paths first fixes it. Measured with kretprobes on a stock v6.17 tree with no other patches applied, on a link that was up and had just carried traffic:
Alternating the two orderings ABBA over three load levels, four teardowns per arm: every teardown failed before the change (21 of 21 that ran), none failed after (0 of 24). The before arms ran short because the link died partway through. The same split shows up when the interface is enslaved to a bond instead of just brought down, which is how I ran into this in the first place. Throughput and latency after the change are unchanged.
Hosts whose routers drain the hop despite the stale descriptor base see no functional difference, since the paths end up deactivated either way.
Detalles técnicos trazas, registros y código del informe original
before: __tb_path_deactivate_hop() returns 0 for the first hop, then
-ETIMEDOUT for the second 500335 us later
after: 0 for both, 525 us apartCVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 8.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.40%
- Percentil entre todas las CVEs puntuadas: 32
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1210Exploitation of Remote Serviceslateral movement25 % - Impacto principal
T1499.004Application or System Exploitationimpact60 %
Red adyacente (AV:A) sugiere T1210, pero es un bug de ordenamiento en teardown de DMA que causa timeout, no explotación activa. El impacto es DoS por agotamiento de recursos (timeout infinito en deactivación).
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
- https://git.kernel.org/stable/c/0da9a6d27155ad072dd76db8cd637feead99a0e0
- https://git.kernel.org/stable/c/103a9b663ac1cacb8465aeff18f84a247154a562
- https://git.kernel.org/stable/c/4dd71cb0d23d40cb58fe4261c7bd183dca66caa0
- https://git.kernel.org/stable/c/68bf02b6b4ad3f748c6db71fd77b6c0402d252f4
- https://git.kernel.org/stable/c/7cce39109206bc5497e0953806563644b88bfc44
- https://git.kernel.org/stable/c/9a482b2b117e5fa656b6d24fc01799e8ac2d4368
- https://git.kernel.org/stable/c/b5a21615f627c48dafaa6ef82a34a5b97a4352aa
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-74691",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 8.8,
"attackVector": "ADJACENT_NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "NONE",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.9,
"exploitabilityScore": 2.8
}
]
},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "e69b6c02b4c3b8d03be7136f90dd9551ad5a5a5e",
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{
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"programFiles": [
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],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.15"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.15",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "6.6.152",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "6.12.104",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "6.18.45",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "7.1.9",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/net/thunderbolt/main.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-08-22T16:16:43.527",
"references": [
{
"url": "https://git.kernel.org/stable/c/0da9a6d27155ad072dd76db8cd637feead99a0e0",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
"url": "https://git.kernel.org/stable/c/103a9b663ac1cacb8465aeff18f84a247154a562",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/7cce39109206bc5497e0953806563644b88bfc44",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/9a482b2b117e5fa656b6d24fc01799e8ac2d4368",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/b5a21615f627c48dafaa6ef82a34a5b97a4352aa",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: thunderbolt: Tear down DMA paths before stopping the rings\n\ntbnet_tear_down() stops both rings and frees their frame buffers before\ncalling tb_xdomain_disable_paths(). tb_ring_stop() zeroes the ring's\ndescriptor base and tbnet_free_buffers() unmaps and frees the pages the\nframes sit in, so by the time __tb_path_deactivate_hop() polls the hop's\n'pending' bit, anything still in flight has nowhere to drain to.\n\nThe teardown sequence has been in this order since the driver was added.\nThe setup path has not: commit ff7cd07f3064 (\"net: thunderbolt: Enable\nDMA paths only after rings are enabled\") moved the path enable to the end\nof tbnet_connected_work() and documented why:\n\n\t/* Both logins successful so enable the rings, high-speed DMA\n\t * paths and start the network device queue.\n\t *\n\t * Note we enable the DMA paths last to make sure we have primed\n\t * the Rx ring before any incoming packets are allowed to\n\t * arrive.\n\t */\n\nTeardown was never updated to match, so the rings and the paths now come\ndown in the same order they go up instead of in reverse.\n\nOn an ASMedia ASM4242 host router the 'pending' bit then never clears:\nevery teardown burns the full 500 ms timeout and\n__tb_path_deactivate_hop() returns -ETIMEDOUT. Raising the timeout to\n5 s does not help, so the hop is not slow to drain, it never drains\nat all.\n\nThe failure is invisible above the thunderbolt core.\n__tb_path_deactivate_hops() is void and only calls tb_port_warn();\ntb_path_deactivate(), tb_tunnel_deactivate() and\n__tb_disconnect_xdomain_paths() are void as well, and\ntb_disconnect_xdomain_paths() ends in an unconditional \"return 0\". So\ntb_xdomain_disable_paths() reports success and the netdev_warn() below\nit never fires. Repeated teardowns eventually take the XDomain control\nchannel down, after which the peer node is gone and only a power cycle\nbrings the controller back.\n\nDeactivating the paths first fixes it. Measured with kretprobes on a\nstock v6.17 tree with no other patches applied, on a link that was up\nand had just carried traffic:\n\n before: __tb_path_deactivate_hop() returns 0 for the first hop, then\n -ETIMEDOUT for the second 500335 us later\n after: 0 for both, 525 us apart\n\nAlternating the two orderings ABBA over three load levels, four\nteardowns per arm: every teardown failed before the change (21 of 21\nthat ran), none failed after (0 of 24). The before arms ran short\nbecause the link died partway through. The same split shows up when\nthe interface is enslaved to a bond instead of just brought down, which\nis how I ran into this in the first place. Throughput and latency after\nthe change are unchanged.\n\nHosts whose routers drain the hop despite the stale descriptor base see\nno functional difference, since the paths end up deactivated either way."
}
],
"lastModified": "2026-08-25T06:18:52.440",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}