CVE-2026-97984

A flaw was found in the Linux kernel's IPv6 networking subsystem. A local user could cause a Denial of Service (DoS) by exploiting an integer overflow in the User Datagram Protocol (UDP) length calculation. When Path MTU Discovery is enabled on a network device configured with an unusually large Maximum Transmission Unit (MTU), transmitting oversized UDP packets can exceed the 16-bit length limit and trigger an internal kernel warning.

A low impact flaw was found in the Linux kernel IPv6 networking subsystem. A local unprivileged user on Red Hat Enterprise Linux 10 or Red Hat In-Vehicle OS 2 could cause a denial of service by opening an IPv6 UDP socket, setting IPV6_MTU_DISCOVER to IPV6_PMTUDISC_DO or IPV6_PMTUDISC_PROBE, and sending an oversized UDP packet over a network device configured with an MTU larger than IP6_MAX_MTU (65535 bytes). Under those conditions the computed UDP length of 65536 overflows the 16-bit length field and triggers a kernel WARN in udp_set_len_short, resulting in failed packet transmission; on systems where panic_on_warn is enabled, this warning escalates to a kernel panic. Red Hat Enterprise Linux 7, 8, and 9, and the OpenShift Container Platform RHEL CoreOS images, are not affected because the vulnerable code is not present in those releases. Red Hat rates this flaw low impact: although the CVSS:3.1 base score is 5.5 (Moderate), exploitation requires local access together with the uncommon configuration of a device MTU above 65535 bytes, and the consequence is limited to a warning and packet failure rather than memory corruption or privilege escalation. Because of this low impact and the impractical preconditions, the fix has been deferred to a future update of the affected releases; the residual risk is a local denial of service confined to systems using such large-MTU network devices.

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 do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.