Improper access control in Linux kernel - CVE-2026-63952
Published: July 20, 2026
Vulnerability identifier: #VU138705
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-63952
CWE-ID: CWE-284
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vendor: Linux Foundation
Affected software:
Linux kernel
Linux kernel
Detailed vulnerability description
The vulnerability allows a local user to bypass write sealing protections and modify a memfd that appears to be write sealed.
The vulnerability exists due to improper access control in memfd_add_seals() in mm/memfd.c when adding SEAL_EXEC to a memfd with writable mappings. A local user can add a seal combination that implies SEAL_WRITE after the writable-mapping check to bypass write sealing protections and modify a memfd that appears to be write sealed.
The issue occurs because SEAL_EXEC implies SEAL_WRITE, but the implied seal was applied only after the check for writable mappings.
How to mitigate CVE-2026-63952
Install security update from vendor's repository.
Sources
- https://git.kernel.org/stable/c/0995d1f79aed8ccbf62056189dd53fd19726ea08
- https://git.kernel.org/stable/c/3b041514cb6eae45869b020f743c14d983363222
- https://git.kernel.org/stable/c/3be2a24f7f72ad7321ed6ad1715b956a4527bcf4
- https://git.kernel.org/stable/c/555702282d4536a865dfffb1cd4f6028f196e7e8
- https://git.kernel.org/stable/c/b3f4f82d1315f1439059a83d1c22c51a5b43d99e