CVE-2026-93783 Bluetooth: RFCOMM: validate skb length in rfcomm_recv_frame
A missing length check in the Linux kernel Bluetooth RFCOMM handler allows attackers to trigger out-of-bounds reads and potential crashes via malformed frames.
- 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-2026-93783?
CVE-2026-93783 is a memory corruption vulnerability in Linux, published on 24 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: RFCOMM: validate skb length in rfcomm_recv_frame
rfcomm_recv_frame() casts skb->data to struct rfcomm_hdr and dereferences hdr->addr and hdr->ctrl without validating skb->len first. A truncated frame with skb->len less than the minimum header size causes an out-of-bounds read of uninitialized memory. Additionally, a zero-length frame causes skb->len-- to underflow to UINT_MAX, making skb_tail_pointer() read far past the buffer.
Commit 23882b828c3c ("Bluetooth: RFCOMM: validate skb length in MCC handlers") fixed the same class of missing-length-check bugs in the MCC sub-handlers, but the top-level rfcomm_recv_frame() was left unfixed. KMSAN reports:
BUG: KMSAN: uninit-value in rfcomm_run ... Uninit was created at: __alloc_skb+0x474/0xb60 vhci_write+0xe9/0x870
Fix this by rejecting frames smaller than sizeof(struct rfcomm_hdr) + 1 (the minimum frame must have a 3-byte header and a 1-byte FCS).
Which versions are affected by CVE-2026-93783?
How do I fix CVE-2026-93783?
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-2026-93783 being exploited?
There is no known exploitation of CVE-2026-93783 in the wild and no public exploit code.
Sources
Also known as AZL-103928, BELL-CVE-2026-93783, DEBIAN-CVE-2026-93783, GHSA-xv96-c36m-qhm7, UBUNTU-CVE-2026-93783.