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
How to mitigate CVE-2026-63803
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3
External References
- https://git.kernel.org/stable/c/508a0139d3bf60f6a03d2fbfb63a89a9463d983a
- https://git.kernel.org/stable/c/5a84398101bf9f11e84b176343e4e3ba83e668c0
- https://git.kernel.org/stable/c/8308122bc9c065b1f376e081ed300129a2ac9545
- https://git.kernel.org/stable/c/a594debfd4e7ec39413647458907f689ef57fd2f
- https://git.kernel.org/stable/c/c64dbef1c0fbd36f9530aa75112acdf6a6d3cfd8
- https://git.kernel.org/stable/c/c78a4e41ab5ead6193ad8a2dd92e8906bae659fa
- https://git.kernel.org/stable/c/ce8f9ddca0c9f217342a8b49efd309aa35b81a36