CVE-2026-80798nfc: llcp: reject PDUs shorter than the LLCP header

Official description

In the Linux kernel, the following vulnerability has been resolved: nfc: llcp: reject PDUs shorter than the LLCP header Every LLCP PDU begins with a two-byte header (DSAP/SSAP + PTYPE), but the receive path never checked that a frame is at least LLCP_HEADER_SIZE bytes before parsing it. nfc_llcp_rx_skb() reads the header via nfc_llcp_ptype()/nfc_llcp_dsap()/ nfc_llcp_ssap(), which dereference pdu->data[0] and pdu->data[1], and a CONNECT or CC PDU then computes tlv_array_len = skb->len - LLCP_HEADER_SIZE; as a size_t and hands it to the TLV walk. When the frame is shorter than the header the subtraction wraps to a huge value and the walk runs far past the buffer, an out-of-bounds read. A nearby NFC device can reach this without authentication; LLCP link activation happens automatically after NFC-DEP. Guard the common receive choke point __nfc_llcp_recv(), shared by both the target (nfc_llcp_data_received()) and initiator (nfc_llcp_recv()) paths, so a short skb is dropped before the rx_work worker parses it. Use pskb_may_pull() rather than a skb->len test so the two header bytes are guaranteed to sit in the skb linear area even for a non-linear skb, matching how the sibling NCI and HCI receive paths validate their headers. Reproduced with a KFENCE out-of-bounds read via /dev/virtual_nci on linux-next. Found by 0sec automated security-research tooling (https://0sec.ai).

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/e6ec76a68dce04884dfeccfe5a5f0e9f67c0ec82
• https://git.kernel.org/stable/c/f36cffea24bf3e2cc29a00d4b51dbcadc087d810
• https://git.kernel.org/stable/c/a7b9b449f5a5132221fff6adc11a9431ab8cd914
• https://git.kernel.org/stable/c/3793d768b40f38bb97265dd5b9a8b8655c4e1b1d
• https://git.kernel.org/stable/c/eab47618e282602197db287ecbd1b09d356a2515
• https://git.kernel.org/stable/c/e969e98410051b1ef8cc318bfe0c7e3f24ec766d
• https://git.kernel.org/stable/c/ae5f20f5842f440b72d030e3a34fe182dd8eae42
• https://git.kernel.org/stable/c/d3d90243393c48146911c67fd3792b549d21d9e6
• https://git.kernel.org/stable/c/95674f506c6376d6722a23144c9acd26609771ed