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Vulnerability · Published Oct 6, 2026 · Assigned by Linux

CVE-2026-98255tcp: exclude old ACKs from tcp fast path

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 7% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS )–Not rated
Exploit odds (30 days)0.2%top 92.8% 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: tcp: exclude old ACKs from tcp fast path Exclude old ACKs before SND.UNA from the tcp fast path as well as ACKs after SND.NXT. Such ACKs will fall through to the slow path, where tcp_ack() performs the appropriate validation and challenge ACK handling according to RFC5961 and Commit 3d501dd326fb1c7 ("tcp: do not accept ACK of bytes we never sent"). This prevents old ACKs from being accepted or modifying connection state as part of the fast path before appropriate ACK validation is applied. In particular, this prevents payload carried by a segment with an excessively old ACK from advancing RCV.NXT before the ACK is rejected.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12linux6.1.190-1DEBIAN-CVE-2026-98255
Debian:13linux6.12.113-1DEBIAN-CVE-2026-98255
Debian:14linux7.2.8-1DEBIAN-CVE-2026-98255
Debian:12linux-6.126.12.113-1~deb12u1DEBIAN-CVE-2026-98255
Ubuntu:22.04:LTSlinux5.15.0-202.212UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinuxno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux7.0.0-42.42UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-allwinner-5.19no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-aws5.15.0-1119.126UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-awsno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-aws7.0.0-1016.17UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-aws-5.19no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-aws-6.14no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-aws-6.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-aws-6.2no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-aws-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-aws-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-aws-7.0no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-azure5.15.0-1125.134UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azureno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-azureno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-azure-5.19no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-6.11no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-6.14no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-6.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-azure-6.2no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-azure-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-azure-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-7.0no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-azure-fde5.15.0-1124.133UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-fdeno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-azure-fdeno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-azure-fde-5.19no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-fde-6.14no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-fde-6.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-azure-fde-6.2no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-azure-fde-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-fde-7.0no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-nvidiano fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-azure-nvidia-6.14no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-gcp5.15.0-1120.130UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-gcpno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-gcp7.0.0-1016.18UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-gcp-5.19no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-gcp-6.11no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-gcp-6.14no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-gcp-6.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-gcp-6.2no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-gcp-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-gcp-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-gcp-7.0no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-gke5.15.0-1115.121UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-gkeno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-gkeno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-gkeop5.15.0-1102.110UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-gkeopno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-hwe-5.19no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-hwe-6.11no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-hwe-6.14no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-hwe-6.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-hwe-6.2no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-hwe-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-hwe-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-hwe-7.07.0.0-42.42~24.04.1UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-ibm5.15.0-1113.117UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-ibmno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-ibm7.0.0-1017.17UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-ibm-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-intel-iot-realtimeno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-intel-iotg5.15.0-1114.120UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-kvm5.15.0-1111.116UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-lowlatency5.15.0-197.207UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-lowlatencyno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-lowlatency-hwe-5.19no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-lowlatency-hwe-6.11no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.2no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-nvidia5.15.0-1114.115UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-nvidiano fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-nvidiano fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-nvidia-6.11no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-nvidia-6.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-nvidia-6.2no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-nvidia-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-nvidia-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-nvidia-7.0no fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-nvidia-bosno fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-nvidia-lowlatencyno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-nvidia-tegra5.15.0-1070.72UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-nvidia-tegrano fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-nvidia-tegra-igx5.15.0-1059.59UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-oem-5.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-oem-6.0no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-oem-6.1no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-oem-6.11no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-oem-6.14no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-oem-6.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-oem-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-oem-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-oem-7.07.0.0-1017.17UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-oracle5.15.0-1116.122UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-oracleno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-oracle7.0.0-1015.16UBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-oracle-6.14no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-oracle-6.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-oracle-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-oracle-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-oracle-7.0no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-raspino fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-raspino fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-raspino fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-raspi-realtimeno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-98255
Ubuntu:26.04:LTSlinux-riscv7.0.0-42.42.1UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-riscv-5.19no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-riscv-6.14no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-riscv-6.17no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-riscv-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-riscv-6.8no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-riscv-7.07.0.0-42.42.1~24.04.1UBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-starfive-5.19no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-starfive-6.2no fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-starfive-6.5no fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-vmwareno fix listedUBUNTU-CVE-2026-98255
Ubuntu:24.04:LTSlinux-xilinxno fix listedUBUNTU-CVE-2026-98255
Ubuntu:22.04:LTSlinux-xilinx-zynqmpno fix listedUBUNTU-CVE-2026-98255

Affected products (as reported)

VendorProductVersions
Linux Linux 31770e34e43d6c8dee129bfee77e56c34e61f0e5 – before 07cacab90290f795bad2e566790f4ba8e84cdf5f31770e34e43d6c8dee129bfee77e56c34e61f0e5 – before 6eb9b697f50b73b9684e466c1e97f4ca8e947a5931770e34e43d6c8dee129bfee77e56c34e61f0e5 – before b86e1e5a4bbcbbccde8b7a3d3486604b581f662831770e34e43d6c8dee129bfee77e56c34e61f0e5 – before 1c8448db5cf35a13d82b0c9004ffdb49358883e731770e34e43d6c8dee129bfee77e56c34e61f0e5 – before 8309dc2cc360056aa9cd2acfbfc25930798c3b6631770e34e43d6c8dee129bfee77e56c34e61f0e5 – before ff037920c688ae6ca1153fec01e90e678271245531770e34e43d6c8dee129bfee77e56c34e61f0e5 – before 8205ac5ddb42a1843fa8d6a8c295b5c7f4f8c6ed31770e34e43d6c8dee129bfee77e56c34e61f0e5 – before f81e6c3fb06327bc49cdd6e559845293ba06a704
Linux Linux 4.14

References