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

6lowpan: fix off-by-one in multicast context address compression

The second memcpy in lowpan_iphc_mcast_ctx_addr_compress() uses
&data[1] as destination and &ipaddr->s6_addr[11] as source, but
both should be offset by one: &data[2] and &ipaddr->s6_addr[12]
respectively.

This off-by-one has two consequences:

1. data[1] is overwritten with s6_addr[11], corrupting the RIID
   field in the compressed multicast address
2. data[5] is never written, so uninitialized kernel stack memory
   is transmitted over the network via lowpan_push_hc_data(),
   leaking kernel stack contents

The correct inline data layout must match what the decompression
function lowpan_uncompress_multicast_ctx_daddr() expects:
data[0..1] = s6_addr[1..2] (flags/scope + RIID)
data[2..5] = s6_addr[12..15] (group ID)

Also zero-initialize the data array as a defensive measure against
similar bugs in the future.

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-53263
• https://git.kernel.org/stable/c/06ce6fc106b16dec9b535950db626261be865e5b
• https://git.kernel.org/stable/c/2a58899d11009bffc7b4b32a571858f381121837
• https://git.kernel.org/stable/c/4485d79617520d84ba5a14515e2b5136007d6deb
• https://git.kernel.org/stable/c/c32f30ef5e66adbfa102348e2e8a23776eb007cb
• https://git.kernel.org/stable/c/da8808463882c3f3c357b072e25053c2121f1419
• https://git.kernel.org/stable/c/da8cbb64b47e9066b40af0de170901caf17b768c
• https://git.kernel.org/stable/c/dcb1bec1c32ee5c3878354e087cf5dbee2b7c7af
• https://git.kernel.org/stable/c/f24a58c72a45f4c109f3557a760cc4b60b7a6037