CVE-2026-90015
In the Linux kernel, the following vulnerability has been resolved:
xhci: fix lost bounce buffers on TDs spanning several ring segments
When a TD reaches a link TRB with data that is not aligned to the endpoint's wMaxPacketSize, xhci_align_td() stages the unalignable tail through the bounce buffer of the ring segment holding that link TRB. xhci_unmap_td_bounce_buffer() later unmaps it and, for IN transfers, copies the data back into the URB's buffer.
The enqueue path records the segment that was bounced in td->bounce_seg, under the assumption that a TD never spans more than two ring segments.
Leer descripción completaMostrar menos
That assumption does not hold: a TD large enough to span three or more segments crosses several link TRBs and can be bounced at each of them. Only the last one survives in td->bounce_seg, so every earlier bounce buffer is neither copied back nor DMA unmapped.
The URB still completes with actual_length equal to the requested length and no error, so the transfer looks successful while a wMaxPacketSize sized hole in the destination buffer silently keeps its previous contents. It also leaks a DMA mapping per dropped bounce.
Any sufficiently large and fragmented bulk transfer can hit this. It was found with a USB mass storage device behind xHCI backing a dm-verity target with 512 byte hash blocks, where the stale data is detected rather than silently consumed. The device enumerates as SuperSpeed, so wMaxPacketSize is 1024, while dm-bufio issues one 512 byte bio per hash block. verity_prefetch_io() makes the block layer merge hundreds of them into a single request of up to 512 scatterlist entries of 512 bytes each. At 256 TRBs per ring segment such a TD spans three segments, and every segment boundary falls on an odd multiple of 512, i.e. unaligned to wMaxPacketSize. dm-bufio then caches a hash block holding stale data and dm-verity declares the metadata block corrupted:
A reproducer running this under qemu is available at https://github.com/baloo/xhci-verity
The bounce state (bounce_buf, bounce_dma, bounce_len, bounce_offs) already lives on the ring segment, so there is nothing extra to track. Keep recording the last bounced segment in td->bounce_seg and, on completion, walk the segments from td->start_seg up to it, unmapping every segment that still has a pending bounce.
Stopping at td->bounce_seg rather than td->end_seg matters: a bounce implies the TD continues past that segment's link TRB, so bounce_seg is always strictly before end_seg, and a later TD may already have started in end_seg and been bounced there. Walking that far would copy a foreign bounce buffer into this URB and unmap it twice. It also keeps the walk correct if a TD ever wraps the whole ring so that end_seg == start_seg.
[mn: Add ring->num_segs check to prevent unlikely infinite for loop.]
Detalles técnicos trazas, registros y código del informe original
device-mapper: verity: 8:2: metadata block 10850 is corrupted
CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.21%
- Percentil entre todas las CVEs puntuadas: 10
- Fecha de la puntuación: 5/10/2026
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).
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/3c9a2b5a4f1183696f02ac280ced1d34afb409b1
- https://git.kernel.org/stable/c/43239fc6dfb62c50ae1b9c0e82bac0f8cd2e285c
- https://git.kernel.org/stable/c/7236bbd2cb7d9fc0eda896bbd34790341e2a4377
- https://git.kernel.org/stable/c/a1629dfb011446d02905778f6df19f14c5f4f3b3
- https://git.kernel.org/stable/c/c8124b28f12dbdd126118e63d0ebf8093a01fb81
- https://git.kernel.org/stable/c/e04d5304a248e5d2a7f4faa87541644bdd320cfb
- https://git.kernel.org/stable/c/efaab8938fb92979be6df359f7d1a43fb7e4717d
- https://git.kernel.org/stable/c/ff44dfb03a293bf30e31f98772a1dd316a6071d1
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-90015",
"cveTags": [],
"metrics": {},
"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": "f9c589e142d04b8a19eb382162f804d17102b5ed",
"lessThan": "c8124b28f12dbdd126118e63d0ebf8093a01fb81",
"versionType": "git"
},
{
"status": "affected",
"version": "f9c589e142d04b8a19eb382162f804d17102b5ed",
"lessThan": "e04d5304a248e5d2a7f4faa87541644bdd320cfb",
"versionType": "git"
},
{
"status": "affected",
"version": "f9c589e142d04b8a19eb382162f804d17102b5ed",
"lessThan": "a1629dfb011446d02905778f6df19f14c5f4f3b3",
"versionType": "git"
},
{
"status": "affected",
"version": "f9c589e142d04b8a19eb382162f804d17102b5ed",
"lessThan": "43239fc6dfb62c50ae1b9c0e82bac0f8cd2e285c",
"versionType": "git"
},
{
"status": "affected",
"version": "f9c589e142d04b8a19eb382162f804d17102b5ed",
"lessThan": "3c9a2b5a4f1183696f02ac280ced1d34afb409b1",
"versionType": "git"
},
{
"status": "affected",
"version": "f9c589e142d04b8a19eb382162f804d17102b5ed",
"lessThan": "efaab8938fb92979be6df359f7d1a43fb7e4717d",
"versionType": "git"
},
{
"status": "affected",
"version": "f9c589e142d04b8a19eb382162f804d17102b5ed",
"lessThan": "7236bbd2cb7d9fc0eda896bbd34790341e2a4377",
"versionType": "git"
},
{
"status": "affected",
"version": "f9c589e142d04b8a19eb382162f804d17102b5ed",
"lessThan": "ff44dfb03a293bf30e31f98772a1dd316a6071d1",
"versionType": "git"
}
],
"programFiles": [
"drivers/usb/host/xhci-ring.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.8"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.8",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.270",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.221",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.188",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.157",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.110",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.51",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.5",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/usb/host/xhci-ring.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-16T11:17:14.210",
"references": [
{
"url": "https://git.kernel.org/stable/c/3c9a2b5a4f1183696f02ac280ced1d34afb409b1",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/43239fc6dfb62c50ae1b9c0e82bac0f8cd2e285c",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/7236bbd2cb7d9fc0eda896bbd34790341e2a4377",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/a1629dfb011446d02905778f6df19f14c5f4f3b3",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/c8124b28f12dbdd126118e63d0ebf8093a01fb81",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/e04d5304a248e5d2a7f4faa87541644bdd320cfb",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/efaab8938fb92979be6df359f7d1a43fb7e4717d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ff44dfb03a293bf30e31f98772a1dd316a6071d1",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxhci: fix lost bounce buffers on TDs spanning several ring segments\n\nWhen a TD reaches a link TRB with data that is not aligned to the\nendpoint's wMaxPacketSize, xhci_align_td() stages the unalignable tail\nthrough the bounce buffer of the ring segment holding that link TRB.\nxhci_unmap_td_bounce_buffer() later unmaps it and, for IN transfers,\ncopies the data back into the URB's buffer.\n\nThe enqueue path records the segment that was bounced in td->bounce_seg,\nunder the assumption that a TD never spans more than two ring segments.\nThat assumption does not hold: a TD large enough to span three or more\nsegments crosses several link TRBs and can be bounced at each of them.\nOnly the last one survives in td->bounce_seg, so every earlier bounce\nbuffer is neither copied back nor DMA unmapped.\n\nThe URB still completes with actual_length equal to the requested length\nand no error, so the transfer looks successful while a wMaxPacketSize\nsized hole in the destination buffer silently keeps its previous\ncontents. It also leaks a DMA mapping per dropped bounce.\n\nAny sufficiently large and fragmented bulk transfer can hit this. It was\nfound with a USB mass storage device behind xHCI backing a dm-verity\ntarget with 512 byte hash blocks, where the stale data is detected rather\nthan silently consumed. The device enumerates as SuperSpeed, so\nwMaxPacketSize is 1024, while dm-bufio issues one 512 byte bio per hash\nblock. verity_prefetch_io() makes the block layer merge hundreds of them\ninto a single request of up to 512 scatterlist entries of 512 bytes each.\nAt 256 TRBs per ring segment such a TD spans three segments, and every\nsegment boundary falls on an odd multiple of 512, i.e. unaligned to\nwMaxPacketSize. dm-bufio then caches a hash block holding stale data and\ndm-verity declares the metadata block corrupted:\n\n device-mapper: verity: 8:2: metadata block 10850 is corrupted\n\nA reproducer running this under qemu is available at\nhttps://github.com/baloo/xhci-verity\n\nThe bounce state (bounce_buf, bounce_dma, bounce_len, bounce_offs)\nalready lives on the ring segment, so there is nothing extra to track.\nKeep recording the last bounced segment in td->bounce_seg and, on\ncompletion, walk the segments from td->start_seg up to it, unmapping\nevery segment that still has a pending bounce.\n\nStopping at td->bounce_seg rather than td->end_seg matters: a bounce\nimplies the TD continues past that segment's link TRB, so bounce_seg is\nalways strictly before end_seg, and a later TD may already have started\nin end_seg and been bounced there. Walking that far would copy a foreign\nbounce buffer into this URB and unmap it twice. It also keeps the walk\ncorrect if a TD ever wraps the whole ring so that end_seg == start_seg.\n\n[mn: Add ring->num_segs check to prevent unlikely infinite for loop.]"
}
],
"lastModified": "2026-09-16T11:17:14.210",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}