CVE-2026-53263 6lowpan: fix off-by-one in multicast context address compression

What is CVE-2026-53263?

CVE-2026-53263 is a medium-severity vulnerability in Linux kernel, published on 25 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

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.

Weakness: CWE-193

Which versions are affected by CVE-2026-53263?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-53263?

Apply the vendor's patch.

Is CVE-2026-53263 being exploited?

There is no known exploitation of CVE-2026-53263 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-90491, BELL-CVE-2026-53263, DEBIAN-CVE-2026-53263, GHSA-fq9x-8g2w-4p5r, ROOT-OS-DEBIAN-11-CVE-2026-53263, ROOT-OS-DEBIAN-12-CVE-2026-53263 and 3 more.