CVE-2025-40043 net: nfc: nci: Add parameter validation for packet data
Insufficient input validation in the Linux kernel NFC driver allows attackers to read uninitialized memory, potentially disclosing sensitive kernel data.
- 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-2025-40043?
CVE-2025-40043 is a high-severity vulnerability in Linux, published on 28 Oct 2025. 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:
net: nfc: nci: Add parameter validation for packet data
Syzbot reported an uninitialized value bug in nci_init_req, which was introduced by commit 5aca7966d2a7 ("Merge tag 'perf-tools-fixes-for-v6.17-2025-09-16' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools").
This bug arises due to very limited and poor input validation that was done at nic_valid_size(). This validation only validates the skb->len (directly reflects size provided at the userspace interface) with the length provided in the buffer itself (interpreted as NCI_HEADER). This leads to the processing of memory content at the address assuming the correct layout per what opcode requires there. This leads to the accesses to buffer of `skb_buff->data` which is not assigned anything yet.
Following the same silent drop of packets of invalid sizes at `nic_valid_size()`, add validation of the data in the respective handlers and return error values in case of failure. Release the skb if error values are returned from handlers in `nci_nft_packet` and effectively do a silent drop
Possible TODO: because we silently drop the packets, the call to `nci_request` will be waiting for completion of request and will face timeouts. These timeouts can get excessively logged in the dmesg. A proper handling of them may require to export `nci_request_cancel` (or propagate error handling from the nft packets handlers).
Which versions are affected by CVE-2025-40043?
How do I fix CVE-2025-40043?
Apply the vendor's patch.
Is CVE-2025-40043 being exploited?
There is no known exploitation of CVE-2025-40043 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40043, DEBIAN-CVE-2025-40043, GHSA-rwhf-69pj-m4jv, ROOT-OS-DEBIAN-11-CVE-2025-40043, ROOT-OS-DEBIAN-12-CVE-2025-40043, ROOT-OS-DEBIAN-13-CVE-2025-40043 and 3 more.