|
ELS
< Back

CVE-2026-63831

Updated on 19 Jul 2026

Severity

8.8 High severity

Details

CVSS score
8.8
CVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Links
NISTCIRCLRHELUbuntu

Overview

About vulnerability

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.

Details

Affected product:
Debian 10 ELS , Debian 11 ELS , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
Affected packages:
linux @ 5.4.0 (+4 more)

Fixes

KernelCare state

Live-patch status from KernelCare for each operating system.

Operating system Status Covered kernels
Debian 11 In Rollout
44 kernels
  • 5.10.46-5
  • 5.10.70-1
  • 5.10.46-4
  • 5.10.84-1
  • 5.10.92-1
  • 5.10.92-2
  • 5.10.103-1
  • 5.10.106-1
  • 5.10.113-1
  • 5.10.120-1
  • 5.10.127-1
  • 5.10.127-2
  • 5.10.136-1
  • 5.10.140-1
  • 5.10.149-1
  • 5.10.149-2
  • 5.10.158-2
  • 5.10.162-1
  • 5.10.179-1
  • 5.10.179-2
  • 5.10.179-3
  • 5.10.179-5
  • 5.10.191-1
  • 5.10.197-1
  • 5.10.178-3
  • 5.10.205-2
  • 5.10.205-1
  • 5.10.209-2
  • 5.10.216-1
  • 5.10.218-1
  • 5.10.221-1
  • 5.10.223-1
  • 5.10.226-1
  • 5.10.234-1
  • 5.10.237-1
  • 5.10.244-1
  • 5.10.247-1
  • 5.10.249-1
  • 5.10.251-1
  • 5.10.251-3
  • 5.10.251-4
  • 5.10.251-5
  • 5.10.257-1
  • 5.10.259-1
Debian 11 cloud Released
24 kernels
  • 5.10.113-1
  • 5.10.179-2
  • 5.10.179-3
  • 5.10.179-5
  • 5.10.191-1
  • 5.10.197-1
  • 5.10.205-2
  • 5.10.209-2
  • 5.10.216-1
  • 5.10.218-1
  • 5.10.221-1
  • 5.10.223-1
  • 5.10.226-1
  • 5.10.234-1
  • 5.10.237-1
  • 5.10.244-1
  • 5.10.247-1
  • 5.10.249-1
  • 5.10.251-1
  • 5.10.251-3
  • 5.10.251-4
  • 5.10.251-5
  • 5.10.257-1
  • 5.10.259-1
Debian 13 Planned —