CVE-2026-46123

Status: Undergoing AnalysisHigh (7.7)—

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: virtio_bt: clamp rx length before skb_put

virtbt_rx_work() calls skb_put(skb, len) where len comes directly from virtqueue_get_buf() with no validation against the buffer we posted to the device. The RX skb is allocated in virtbt_add_inbuf() and exposed to virtio as exactly 1000 bytes via sg_init_one().

Checking len against skb_tailroom(skb) is not sufficient because alloc_skb() can leave more tailroom than the 1000 bytes actually handed to the device. A malicious or buggy backend can therefore report used.len between 1001 and skb_tailroom(skb), causing skb_put() to include uninitialized kernel heap bytes that were never written by the device.

Read full descriptionShow less

The same path also accepts len == 0, in which case skb_put(skb, 0) leaves the skb empty but virtbt_rx_handle() still reads the pkt_type byte from skb->data, consuming uninitialized memory.

Define VIRTBT_RX_BUF_SIZE once and reuse it in alloc_skb() and sg_init_one(), and gate virtbt_rx_work() on that same constant so the bound checked matches the buffer actually exposed to the device. Reject used.len == 0 in the same gate so an empty completion can no longer reach virtbt_rx_handle().

Use bt_dev_err_ratelimited() because the length value comes from an untrusted backend that can otherwise flood the kernel log.

Same class of bug as commit c04db81cd028 ("net/9p: Fix buffer overflow in USB transport layer"), which hardened the USB 9p transport against unchecked device-reported length.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Base score: 7.7

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.19%
Percentile among all scored CVEs: 8
Score date: 10/6/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1068 Exploitation for Privilege Escalationprivilege escalation85 %
Primary impactT1005 Data from Local Systemcollection90 %
Secondary impactT1059 Command and Scripting Interpreterexecution70 %

Vulnerabilidad local (AV:L, PR:N) sin interacción que permite lectura de memoria kernel no inicializada (CWE-787, buffer over-read) y potencial ejecución de código mediante corrupción de heap en el controlador Bluetooth virtio del kernel Linux.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Execution Prevention Threat Intelligence Program Restrict Web-Based Content Privileged Account Management Limit Software Installation Behavior Prevention on Endpoint

Affected technologies (1)

Linux — Linux Kernel

CWEs

CWE-787

References

Raw JSON (NVD)

Show

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: virtio_bt: clamp rx length before skb_put\n\nvirtbt_rx_work() calls skb_put(skb, len) where len comes directly\nfrom virtqueue_get_buf() with no validation against the buffer we\nposted to the device. The RX skb is allocated in virtbt_add_inbuf()\nand exposed to virtio as exactly 1000 bytes via sg_init_one().\n\nChecking len against skb_tailroom(skb) is not sufficient because\nalloc_skb() can leave more tailroom than the 1000 bytes actually\nhanded to the device. A malicious or buggy backend can therefore\nreport used.len between 1001 and skb_tailroom(skb), causing skb_put()\nto include uninitialized kernel heap bytes that were never written by\nthe device.\n\nThe same path also accepts len == 0, in which case skb_put(skb, 0)\nleaves the skb empty but virtbt_rx_handle() still reads the pkt_type\nbyte from skb->data, consuming uninitialized memory.\n\nDefine VIRTBT_RX_BUF_SIZE once and reuse it in alloc_skb() and\nsg_init_one(), and gate virtbt_rx_work() on that same constant so\nthe bound checked matches the buffer actually exposed to the device.\nReject used.len == 0 in the same gate so an empty completion can\nno longer reach virtbt_rx_handle().\n\nUse bt_dev_err_ratelimited() because the length value comes from an\nuntrusted backend that can otherwise flood the kernel log.\n\nSame class of bug as commit c04db81cd028 (\"net/9p: Fix buffer\noverflow in USB transport layer\"), which hardened the USB 9p\ntransport against unchecked device-reported length."
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