---
id: CVE-2026-90055
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  usb: atm: usbatm: fix invalid ci_range initialization

  syzbot reported a shift-out-of-bounds in __vcc_connect():

    UBSAN: shift-out-of-bounds in net/atm/common.c:382:3…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  usb: atm: usbatm: fix invalid ci_range initialization

  syzbot reported a shift-out-of-bounds in __vcc_connect():

    UBSAN: shift-out-of-bounds in net/atm/common.c:382:3…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= c59bba75fa500f13ef14215d599ee0d7faa1b954 <
    8442586526c406527bf31206e538c0ce6bc672e6
  - >-
    Linux >= c59bba75fa500f13ef14215d599ee0d7faa1b954 <
    561cbd6d49022c9a383e22a39c87a165a4d39f9c
  - >-
    Linux >= c59bba75fa500f13ef14215d599ee0d7faa1b954 <
    76bc7c3a44856744b64aa91d9afe6d9522a78c42
  - >-
    Linux >= c59bba75fa500f13ef14215d599ee0d7faa1b954 <
    7baa0c92be39eb3da755ed6f200497a57078c47b
  - >-
    Linux >= c59bba75fa500f13ef14215d599ee0d7faa1b954 <
    1e964d414bfd9f8dfe9948d08e4b9dda4ed2e422
  - >-
    Linux >= c59bba75fa500f13ef14215d599ee0d7faa1b954 <
    ff7f77a234f7b74e5955a6e34fa74eca4c9ca44c
  - >-
    Linux >= c59bba75fa500f13ef14215d599ee0d7faa1b954 <
    75667703115154a4fd9cf259d4f826d8729cbcda
  - >-
    Linux >= c59bba75fa500f13ef14215d599ee0d7faa1b954 <
    a60fd8c6dbaa76da4163cf225ed2b9e982540f39
  - Linux 2.6.13
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:16:54.020'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-90055'
references:
  - url: 'https://git.kernel.org/stable/c/1e964d414bfd9f8dfe9948d08e4b9dda4ed2e422'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/561cbd6d49022c9a383e22a39c87a165a4d39f9c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/75667703115154a4fd9cf259d4f826d8729cbcda'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/76bc7c3a44856744b64aa91d9afe6d9522a78c42'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7baa0c92be39eb3da755ed6f200497a57078c47b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8442586526c406527bf31206e538c0ce6bc672e6'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a60fd8c6dbaa76da4163cf225ed2b9e982540f39'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ff7f77a234f7b74e5955a6e34fa74eca4c9ca44c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.903Z'
epss: 0.0022
epssPercentile: 0.11068
---

## Overview

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

usb: atm: usbatm: fix invalid ci_range initialization

syzbot reported a shift-out-of-bounds in __vcc_connect():

  UBSAN: shift-out-of-bounds in net/atm/common.c:382:32
  shift exponent -1 is negative
  CPU: 0 UID: 0 PID: 5987 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full)
  Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
  Call Trace:
   <TASK>
   dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
   ubsan_epilogue+0xa/0x30 lib/ubsan.c:233
   __ubsan_handle_shift_out_of_bounds+0x36d/0x400 lib/ubsan.c:494
   __vcc_connect+0x14b4/0x19c0 net/atm/common.c:382
   vcc_connect+0x328/0x8f0 net/atm/common.c:498
   pvc_bind+0x272/0x380 net/atm/pvc.c:52
   __sys_bind+0x2e3/0x410 net/socket.c:1976
   __x64_sys_bind+0x7a/0x90 net/socket.c:1979
   ...

ATM device ci_range fields (vpi_bits and vci_bits) represent the
number of bits supported for VPI and VCI addressing on the device.
net/atm/common.c directly uses these fields as bit shift counts:
  vpi >> dev->ci_range.vpi_bits
  vci >> dev->ci_range.vci_bits
  1 << vcc->dev->ci_range.vpi_bits
  1 << vcc->dev->ci_range.vci_bits

usbatm_atm_init() sets ci_range.vpi_bits and ci_range.vci_bits to
ATM_CI_MAX (-1), which is defined in <uapi/linux/atmdev.h> as a
sentinel value for userspace ATM_SETCIRANGE requests, not a valid bit
count. Shifting by -1 is undefined behavior and triggers UBSAN
warnings.

ATM UNI cell headers allow up to 8 bits for VPI (0..255) and 16 bits
for VCI (0..65535). Initialize vpi_bits to 8 and vci_bits to 16, as
done by solos-pci.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.