CVE-2026-63831

Description

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 skb's 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 skb's 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 skb's 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 clone's 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.

Predictions

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63831
• 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
• https://www.suse.com/security/cve/CVE-2026-63831.html