---
id: CVE-2026-31513
title: 'Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req

  Syzbot reported a KASAN stack-out-of-bounds read in l2cap_build_cmd()
  that is triggered by a mal…
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 935f324e4b2461df2cf7f02b4195082b4304c708 <
    c8e1a27edb8b4e5afb56b384acd7b6c2dec1b7cc
  - >-
    Linux >= e981a9392800ce2c5bca196a6ab2c55e9370efaa <
    5b35f8211a913cfe7ab9d54fa36a272d2059a588
  - >-
    Linux >= f3fdf2e7276a3edc5df55454275da20eac186970 <
    a3d9c50d69785ae02e153f000da1b5fd6dbfdf1b
  - >-
    Linux >= c28d2bff70444a85b3b86aaf241ece9408c7858c <
    9d87cb22195b2c67405f5485d525190747ad5493
  - Linux >= 6.12.75 < 6.12.80
  - Linux >= 6.18.16 < 6.18.21
  - Linux >= 6.19.6 < 6.19.11
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-16T15:10:31.040486Z'
published: '2026-04-22'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:20:14.252Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31513'
references:
  - url: 'https://git.kernel.org/stable/c/c8e1a27edb8b4e5afb56b384acd7b6c2dec1b7cc'
  - url: 'https://git.kernel.org/stable/c/5b35f8211a913cfe7ab9d54fa36a272d2059a588'
  - url: 'https://git.kernel.org/stable/c/a3d9c50d69785ae02e153f000da1b5fd6dbfdf1b'
  - url: 'https://git.kernel.org/stable/c/9d87cb22195b2c67405f5485d525190747ad5493'
tags:
  - cve.org
epss: 0.00385
epssPercentile: 0.31024
ingestedAt: '2026-10-16T17:24:46.658Z'
---

## Overview

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

Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req

Syzbot reported a KASAN stack-out-of-bounds read in l2cap_build_cmd()
that is triggered by a malformed Enhanced Credit Based Connection Request.

The vulnerability stems from l2cap_ecred_conn_req(). The function allocates
a local stack buffer (`pdu`) designed to hold a maximum of 5 Source Channel
IDs (SCIDs), totaling 18 bytes. When an attacker sends a request with more
than 5 SCIDs, the function calculates `rsp_len` based on this unvalidated
`cmd_len` before checking if the number of SCIDs exceeds
L2CAP_ECRED_MAX_CID.

If the SCID count is too high, the function correctly jumps to the
`response` label to reject the packet, but `rsp_len` retains the
attacker's oversized value. Consequently, l2cap_send_cmd() is instructed
to read past the end of the 18-byte `pdu` buffer, triggering a
KASAN panic.

Fix this by moving the assignment of `rsp_len` to after the `num_scid`
boundary check. If the packet is rejected, `rsp_len` will safely
remain 0, and the error response will only read the 8-byte base header
from the stack.

## Affected

- `Linux >= 935f324e4b2461df2cf7f02b4195082b4304c708 < c8e1a27edb8b4e5afb56b384acd7b6c2dec1b7cc`
- `Linux >= e981a9392800ce2c5bca196a6ab2c55e9370efaa < 5b35f8211a913cfe7ab9d54fa36a272d2059a588`
- `Linux >= f3fdf2e7276a3edc5df55454275da20eac186970 < a3d9c50d69785ae02e153f000da1b5fd6dbfdf1b`
- `Linux >= c28d2bff70444a85b3b86aaf241ece9408c7858c < 9d87cb22195b2c67405f5485d525190747ad5493`
- `Linux >= 6.12.75 < 6.12.80`
- `Linux >= 6.18.16 < 6.18.21`
- `Linux >= 6.19.6 < 6.19.11`

## Remediation

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