CVE-2026-43186

A flaw was found in the Linux kernel's IPv6 In-situ Operations, Administration, and Maintenance (IOAM) functionality. A remote attacker can send a specially crafted packet that manipulates the nodelen field while processing trace data. This manipulation leads to a heap buffer overflow, causing approximately 100 bytes to be written past the allocated memory region. This memory corruption can result in a kernel panic, effectively leading to a Denial of Service (DoS) for the affected system.

A crafted IPv6 IOAM Pre-allocated Trace option can make the receive path trust an inconsistent nodelen value while type bits request more trace data than the allocated area can hold. This can cause __ioam6_fill_trace_data to write about 100 bytes past the IOAM trace area into adjacent heap memory such as skb_shared_info, leading to kernel memory corruption and panic. For the CVSS the PR:N is used because a packet sender does not need credentials on the victim when IPv6 IOAM processing and a matching namespace are configured. The issue is network reachable under IOAM deployment preconditions only. Impact is at least remote denial of service via kernel crash, and worst case may allow confidentiality or integrity impact because the primitive is a heap out-of-bounds write in a packet receive path. However, practical attack exposure is limited because no exploit primitive beyond denial of service has been demonstrated. The bug is specific to IPv6 IOAM processing, which is not commonly deployed and is typically disabled by default on most general-purpose servers. Systems that do not enable IOAM processing on the receive path are generally not reachable through this issue.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.