CVE-2026-532636lowpan: fix off-by-one in multicast context address compression

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/f24a58c72a45f4c109f3557a760cc4b60b7a6037
• https://git.kernel.org/stable/c/da8cbb64b47e9066b40af0de170901caf17b768c
• https://git.kernel.org/stable/c/4485d79617520d84ba5a14515e2b5136007d6deb
• https://git.kernel.org/stable/c/06ce6fc106b16dec9b535950db626261be865e5b
• https://git.kernel.org/stable/c/dcb1bec1c32ee5c3878354e087cf5dbee2b7c7af
• https://git.kernel.org/stable/c/c32f30ef5e66adbfa102348e2e8a23776eb007cb
• https://git.kernel.org/stable/c/da8808463882c3f3c357b072e25053c2121f1419
• https://git.kernel.org/stable/c/2a58899d11009bffc7b4b32a571858f381121837
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html