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Vulnerability · Published Sep 25, 2026 · Assigned by Linux

CVE-2026-97984net: ipv6: Fix UDP length overflow with PMTU discover and big MTU

Unrated

In plain English

A security flaw in Linux from Linux. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 6% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS )–Not rated
Exploit odds (30 days)0.2%top 93.9% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official description

In the Linux kernel, the following vulnerability has been resolved: net: ipv6: Fix UDP length overflow with PMTU discover and big MTU This commit bounds cork->base.fragsize to IP6_MAX_MTU for UDP sockets to avoid a possible overflow of UDP length that triggers a WARN in udp_set_len_short when setsockopt IPV6_MTU_DISCOVER is set to IPV6_PMTUDISC_DO or IPV6_PMTUDISC_PROBE, and a large packet is sent over a netdev with an unusually large MTU. Steps to reproduce (included in the new selftest): 1. Set device MTU bigger than IP6_MAX_MTU. cork->base.fragsize will be set to that MTU in ip6_setup_cork. 2. Set IPV6_MTU_DISCOVER to IPV6_PMTUDISC_PROBE or IPV6_PMTUDISC_DO. It lets maxnonfragsize be set to device MTU (cork->fragsize) in __ip6_append_data, rather than to IP6_MAX_MTU. 3. Send 65528 bytes of payload (+8 bytes of UDP header, +40 bytes of IPv6 header). Device MTU allows it (it's only one byte bigger than IP6_MAX_MTU, and the device MTU is bigger than that). 4. The UDP length in the built packet is 65536, which overflows the 16-bit length field and triggers the WARN in udp_set_len_short. To avoid breaking sending UDP jumbograms over raw IPv6 sockets, limit the change to UDP sockets only. The original overflow bug with IPv6 and IPV6_PMTUDISC_DO seems to predate git history (verified reproduction on 2.6.21), was fixed later, and then reappeared in commit 427faee167bc ("net: ipv6: introduce ip6_dst_mtu_maybe_forward"), which is chosen as the Fixes tag here. The overflow with IPV6_PMTUDISC_PROBE reproduces since its introduction in commit 628a5c561890 ("[INET]: Add IP(V6)_PMTUDISC_RPOBE").

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12linuxno fix listedDEBIAN-CVE-2026-97984
Debian:13linux6.12.111-1DEBIAN-CVE-2026-97984
Debian:14linux7.2.7-1DEBIAN-CVE-2026-97984
Debian:12linux-6.126.12.111-1~deb12u1DEBIAN-CVE-2026-97984
Ubuntu:22.04:LTSlinuxno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinuxno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux7.0.0-42.42UBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-allwinner-5.19no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-awsno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-awsno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-aws7.0.0-1016.17UBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-aws-5.19no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-aws-6.14no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-aws-6.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-aws-6.2no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-aws-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-aws-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-aws-7.0no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-azureno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azureno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-azureno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-azure-5.19no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-6.11no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-6.14no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-6.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-azure-6.2no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-azure-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-azure-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-7.0no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-azure-fdeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-fdeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-azure-fdeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-azure-fde-5.19no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-fde-6.14no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-fde-6.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-azure-fde-6.2no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-azure-fde-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-fde-7.0no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-nvidiano fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-azure-nvidia-6.14no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-gcpno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-gcpno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-gcp7.0.0-1016.18UBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-gcp-5.19no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-gcp-6.11no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-gcp-6.14no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-gcp-6.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-gcp-6.2no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-gcp-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-gcp-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-gcp-7.0no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-gkeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-gkeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-gkeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-gkeopno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-gkeopno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-hwe-5.19no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-hwe-6.11no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-hwe-6.14no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-hwe-6.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-hwe-6.2no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-hwe-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-hwe-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-hwe-7.07.0.0-42.42~24.04.1UBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-ibmno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-ibmno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-ibm7.0.0-1017.17UBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-ibm-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-intel-iot-realtimeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-intel-iotgno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-kvmno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-lowlatencyno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-lowlatencyno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-lowlatency-hwe-5.19no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-lowlatency-hwe-6.11no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.2no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-nvidiano fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-nvidiano fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-nvidiano fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-nvidia-6.11no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-nvidia-6.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-nvidia-6.2no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-nvidia-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-nvidia-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-nvidia-7.0no fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-nvidia-bosno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-nvidia-lowlatencyno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-nvidia-tegrano fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-nvidia-tegrano fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-nvidia-tegra-igxno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-oem-5.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-oem-6.0no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-oem-6.1no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-oem-6.11no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-oem-6.14no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-oem-6.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-oem-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-oem-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-oem-7.07.0.0-1017.17UBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-oracleno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-oracleno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-oracle7.0.0-1015.16UBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-oracle-6.14no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-oracle-6.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-oracle-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-oracle-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-oracle-7.0no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-raspino fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-raspino fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-raspino fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-raspi-realtimeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-97984
Ubuntu:26.04:LTSlinux-riscv7.0.0-42.42.1UBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-riscv-5.19no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-riscv-6.14no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-riscv-6.17no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-riscv-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-riscv-6.8no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-riscv-7.07.0.0-42.42.1~24.04.1UBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-starfive-5.19no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-starfive-6.2no fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-starfive-6.5no fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-vmwareno fix listedUBUNTU-CVE-2026-97984
Ubuntu:24.04:LTSlinux-xilinxno fix listedUBUNTU-CVE-2026-97984
Ubuntu:22.04:LTSlinux-xilinx-zynqmpno fix listedUBUNTU-CVE-2026-97984

Affected products (as reported)

VendorProductVersions
Linux Linux 427faee167bce4ccb0b22f6815a9ac509e31d4c3 – before 1dd562f3019019ffdf4b396570613053facda9ee427faee167bce4ccb0b22f6815a9ac509e31d4c3 – before 1d56a00ec91f2885c64ea5b8cea18cb746b91bbb427faee167bce4ccb0b22f6815a9ac509e31d4c3 – before ce66352d3eb21825410af8b91db7cc4bb8e22c98427faee167bce4ccb0b22f6815a9ac509e31d4c3 – before e01b7c176d9af2b7c22bb3fe12cf9a7904f99fdc427faee167bce4ccb0b22f6815a9ac509e31d4c3 – before 0ae10b6be49b425827659b23bcce498f80eb7182
Linux Linux 5.15

References