# CVE-2026-98108: Bluetooth: L2CAP: fix chan mode for LE_CONN_REQ + EXT_FLOWCTL pchan

> A flaw in the Linux kernel Bluetooth L2CAP module allows out-of-bounds writes, potentially leading to code execution or system crashes.

- **Severity:** High 7.5 (`CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104427, BELL-CVE-2026-98108, DEBIAN-CVE-2026-98108, GHSA-q3c9-52vx-cgp8, UBUNTU-CVE-2026-98108

## What is CVE-2026-98108?

CVE-2026-98108 is a high-severity memory corruption vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

Bluetooth: L2CAP: fix chan mode for LE_CONN_REQ + EXT_FLOWCTL pchan

l2cap_new_connection() sets default value of channel mode to match the
parent channel.  l2cap_le_connect_req() left this at the default, and
created L2CAP_MODE_EXT_FLOWCTL channels if listening pchan has that
mode.  This causes FLAG_DEFER_SETUP channels to reply to
L2CAP_LE_CONN_REQ with L2CAP_ECRED_CONN_RSP, which is incorrect.

It can also result to stack OOB write (of l2cap_alloc_cid determined
values) in l2cap_ecred_rsp_defer(), as l2cap_le_connect_req() does not
limit maximum number of deferred channels or check for duplicate ident.

Fix by setting chan->mode correctly in l2cap_le_connect_req().

Also check channel mode in l2cap_ecred_rsp_defer(), and do WARN_ON_ONCE
instead of OOB write to make it less brittle.

## Which versions are affected by CVE-2026-98108?


## How do I fix CVE-2026-98108?

Apply the vendor's patch.

## Is CVE-2026-98108 being exploited?

There is no known exploitation of CVE-2026-98108 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98108 and fix it if it is affected.

What it is: CVE-2026-98108 is a high-severity memory corruption vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98108 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98108/ (Markdown: https://insights.sbomify.com/CVE-2026-98108/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98108
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98108
- OSV: https://osv.dev/vulnerability/CVE-2026-98108

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98108/
Summaries are generated and may contain mistakes; the official description above is the record.