Use-after-free in Linux kernel - CVE-2026-63803

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Main Vulnerability Database Vulnerabilities #VU138858

Use-after-free in Linux kernel - CVE-2026-63803

Published: July 21, 2026


Vulnerability identifier: #VU138858
CSH Severity: Low
CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-63803
CWE-ID: CWE-416
Exploitation vector: Local access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to a use-after-free in the hdlc ppp per-protocol timer handling when detaching the ppp protocol or re-attaching it while timers are still active. A local user can trigger protocol teardown while a timer callback is executing to cause a denial of service.

The issue affects LCP, IPCP, and IPV6CP control protocol timers embedded in the PPP state.


Affected software

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-kvm (Ubuntu package)
linux-gcp (Ubuntu package)
linux-aws (Ubuntu package)
linux-azure (Ubuntu package)
linux-raspi (Ubuntu package)
linux-oracle (Ubuntu package)
linux-lowlatency (Ubuntu package)
linux-gke (Ubuntu package)
linux-aws-5.15 (Ubuntu package)
linux-lowlatency-hwe-5.15 (Ubuntu package)
linux-hwe-5.15 (Ubuntu package)
linux-fips (Ubuntu package)
linux-azure-5.15 (Ubuntu package)
linux-intel-iotg (Ubuntu package)
linux-azure-fde-5.15 (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-nvidia-tegra-igx (Ubuntu package)
linux-realtime (Ubuntu package)
linux-nvidia-tegra (Ubuntu package)
linux-gkeop (Ubuntu package)
linux-ibm-5.15 (Ubuntu package)
linux-ibm (Ubuntu package)
linux-intel-iotg-5.15 (Ubuntu package)
linux-oracle-5.15 (Ubuntu package)
linux-gcp-5.15 (Ubuntu package)
linux-nvidia-tegra-5.15 (Ubuntu package)
linux-xilinx-zynqmp (Ubuntu package)
linux-intel-iot-realtime (Ubuntu package)
linux-gcp-fips (Ubuntu package)
linux-aws-fips (Ubuntu package)
linux-azure-fips (Ubuntu package)
linux-azure-fde (Ubuntu package)
linux-hwe-6.8 (Ubuntu package)
linux-lowlatency-hwe-6.8 (Ubuntu package)
linux-azure-fde-6.8 (Ubuntu package)
linux-aws-6.8 (Ubuntu package)
linux-azure-6.8 (Ubuntu package)
linux-oracle-6.8 (Ubuntu package)
linux-nvidia-lowlatency (Ubuntu package)
linux-ibm-6.8 (Ubuntu package)
linux-gcp-6.8 (Ubuntu package)
linux-raspi-realtime (Ubuntu package)
linux-realtime-6.8 (Ubuntu package)
linux-nvidia-bos (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-azure-7.0 (Ubuntu package)
linux-oracle-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux-aws-7.0 (Ubuntu package)
linux-nvidia-7.0 (Ubuntu package)

How to mitigate CVE-2026-63803

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - addressed in versions 5.15.0-198.208, 6.8.0-147.147, 7.0.0-31.31
linux-kvm (Ubuntu package) - update to 5.15.0-1109.114
linux-gcp (Ubuntu package) - addressed in versions 5.15.0-1118.128, 6.8.0-1071.79, 7.0.0-1011.11
linux-aws (Ubuntu package) - addressed in versions 5.15.0-1117.124, 6.8.0-1067.70, 7.0.0-1012.12
linux-azure (Ubuntu package) - addressed in versions 5.15.0-1123.132, 6.8.0-1071.79, 7.0.0-1014.14
linux-raspi (Ubuntu package) - addressed in versions 5.15.0-1113.116, 6.8.0-1068.72, 7.0.0-1019.19
linux-oracle (Ubuntu package) - addressed in versions 5.15.0-1114.120, 6.8.0-1064.67, 7.0.0-1011.11
linux-lowlatency (Ubuntu package) - addressed in versions 5.15.0-195.205, 6.8.0-147.147.1
linux-gke (Ubuntu package) - addressed in versions 5.15.0-1113.119, 6.8.0-1066.74, 7.0.0-1006.7
linux-aws-5.15 (Ubuntu package) - update to 5.15.0-1117.124~20.04.1
linux-lowlatency-hwe-5.15 (Ubuntu package) - update to 5.15.0-195.205~20.04.1
linux-hwe-5.15 (Ubuntu package) - update to 5.15.0-198.208~20.04.1
linux-fips (Ubuntu package) - addressed in versions 5.15.0-198.208+fips1, 6.8.0-147.147+fips1
linux-azure-5.15 (Ubuntu package) - update to 5.15.0-1123.132~20.04.1
linux-intel-iotg (Ubuntu package) - update to 5.15.0-1112.118
linux-azure-fde-5.15 (Ubuntu package) - update to 5.15.0-1122.131~20.04.1
linux-nvidia (Ubuntu package) - addressed in versions 5.15.0-1112.113, 6.8.0-1067.70, 7.0.0-1018.18
linux-nvidia-tegra-igx (Ubuntu package) - update to 5.15.0-1059.59
linux-realtime (Ubuntu package) - addressed in versions 5.15.0-1116.125, 6.8.1-1062.63, 7.0.0-31.31.1
linux-nvidia-tegra (Ubuntu package) - addressed in versions 5.15.0-1070.72, 6.8.0-1036.39
linux-gkeop (Ubuntu package) - addressed in versions 5.15.0-1100.108, 6.8.0-1052.56
linux-ibm-5.15 (Ubuntu package) - update to 5.15.0-1111.115~20.04.1
linux-ibm (Ubuntu package) - addressed in versions 5.15.0-1111.115, 6.8.0-1067.68, 7.0.0-1013.13
linux-intel-iotg-5.15 (Ubuntu package) - update to 5.15.0-1112.118~20.04.1
linux-oracle-5.15 (Ubuntu package) - update to 5.15.0-1114.120~20.04.1
linux-gcp-5.15 (Ubuntu package) - update to 5.15.0-1118.128~20.04.1
linux-nvidia-tegra-5.15 (Ubuntu package) - update to 5.15.0-1070.72~20.04.1
linux-xilinx-zynqmp (Ubuntu package) - update to 5.15.0-1080.84
linux-intel-iot-realtime (Ubuntu package) - update to 5.15.0-1109.111
linux-gcp-fips (Ubuntu package) - addressed in versions 5.15.0-1118.128+fips1, 6.8.0-1071.79+fips1
linux-aws-fips (Ubuntu package) - addressed in versions 5.15.0-1117.124+fips1, 6.8.0-1067.70+fips1
linux-azure-fips (Ubuntu package) - addressed in versions 5.15.0-1123.132+fips1, 6.8.0-1071.79+fips1
linux-azure-fde (Ubuntu package) - update to 6.8.0-1069.76
linux-hwe-6.8 (Ubuntu package) - update to 6.8.0-149.149~22.04.1
linux-lowlatency-hwe-6.8 (Ubuntu package) - update to 6.8.0-149.149.1~22.04.1
linux-azure-fde-6.8 (Ubuntu package) - update to 6.8.0-1071.78~22.04.1
linux-aws-6.8 (Ubuntu package) - update to 6.8.0-1069.74~22.04.1
linux-azure-6.8 (Ubuntu package) - update to 6.8.0-1073.82~22.04.1
linux-oracle-6.8 (Ubuntu package) - update to 6.8.0-1067.71~22.04.1
linux-nvidia-lowlatency (Ubuntu package) - update to 6.8.0-1067.70.1
linux-ibm-6.8 (Ubuntu package) - update to 6.8.0-1069.70~22.04.1
linux-gcp-6.8 (Ubuntu package) - update to 6.8.0-1073.81~22.04.1
linux-raspi-realtime (Ubuntu package) - update to 6.8.0-2056.58
linux-realtime-6.8 (Ubuntu package) - update to 6.8.1-1064.65~22.04.1
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2018.18
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-31.31~24.04.1
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-azure-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1
linux-oracle-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1013.13
linux-aws-7.0 (Ubuntu package) - update to 7.0.0-1012.12~24.04.1
linux-nvidia-7.0 (Ubuntu package) - update to 7.0.0-1018.18~24.04.1

External References

Related Security Bulletins