CVE-2026-63952

Description

In the Linux kernel, the following vulnerability has been resolved: memfd: deny writeable mappings when implying SEAL_WRITE When SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the implied seal is set after the check that makes sure the memfd can not have any writable mappings. This means one can use SEAL_EXEC to apply SEAL_WRITE while having writeable mappings. This breaks the contract that SEAL_WRITE provides and can be used by an attacker to pass a memfd that appears to be write sealed but can still be modified arbitrarily. Fix this by adding the implied seals before the call for mapping_deny_writable() is done.

References

• 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