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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
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.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-98108 being exploited?
There is no known exploitation of CVE-2026-98108 in the wild and no public exploit code.
Sources
Also known as AZL-104427, BELL-CVE-2026-98108, DEBIAN-CVE-2026-98108, GHSA-q3c9-52vx-cgp8, UBUNTU-CVE-2026-98108.