CVE-2026-63831

In the Linux kernel, the following vulnerability has been resolved:

mac802154: llsec: add skb_cow_data() before in-place crypto

llsec_do_encrypt_unauth(), llsec_do_encrypt_auth(), llsec_do_decrypt_unauth(), and llsec_do_decrypt_auth() all perform in-place cryptographic transformations on skb data. They build a scatterlist with sg_init_one() pointing into the skbs linear data area and then pass the same scatterlist as both src and dst to the crypto API (e.g. crypto_skcipher_encrypt/decrypt, crypto_aead_encrypt/decrypt).

On the RX path, __ieee802154_rx_handle_packet() clones the received skb before handing it to each subscriber via ieee802154_subif_frame(). The cloned skb shares the same underlying data buffer via reference counting. When llsec_do_decrypt() subsequently modifies this shared buffer in place, it corrupts data that other clones – potentially belonging to other sockets or subsystems – still reference.

On the TX path, similar data sharing can occur when an skbs head has been cloned (skb_cloned() returns true).

The fix is to call skb_cow_data() before performing any in-place crypto operation. skb_cow_data() ensures that the skbs data area is not shared: if the skb head is cloned or the data spans multiple fragments, it copies the data into a private buffer that can be safely modified in place. This is the same pattern used by:

• ESP (net/ipv4/esp4.c, net/ipv6/esp6.c)
• MACsec (drivers/net/macsec.c)
• WireGuard (drivers/net/wireguard/receive.c)
• TIPC (net/tipc/crypto.c)

Without this guard, in-place crypto on shared skb data leads to:

• Silent data corruption of other skb clones
• Use-after-free when the crypto API scatterwalk writes through a page that has already been freed by another clones kfree_skb()
• Kernel crashes under concurrent 802.15.4 traffic with security enabled (KASAN/KMSAN reports slab-use-after-free)

Found by 0sec (https://0sec.ai) using automated source analysis.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/3a2b378b3a9ca75d3518d879148d2ad25b5714a9
• https://git.kernel.org/stable/c/7a831bcd0486788283ef35e396d4282ee01bb0d5
• https://git.kernel.org/stable/c/84a04eb5b210643bd67aab81ff805d32f62aa865
• https://git.kernel.org/stable/c/86d531337ea1ba02d9f2bc830d07c683d9bfaade
• https://git.kernel.org/stable/c/993fd674fe85d114e6a8d3963033d4fbbc2170a8
• https://git.kernel.org/stable/c/bd968bdd568beacfdf98ec537a87527e85f1d0cf
• https://git.kernel.org/stable/c/e28e7fd34c449028325322a3f5127b92594b7396
• https://git.kernel.org/stable/c/ff976ef7c39199ebff33c18034636595016db9f0