CVE-2026-93783

Summary

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).

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/67dc3b40fae71b6b11c71e7ff69bac0758818c05
• https://git.kernel.org/stable/c/bbc310caa2b6bf5fe42896ba27da0fbc12e4ac51
• https://git.kernel.org/stable/c/b230e5bf501c5edaf2eb0991cb862ac142031d4b

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