CVE-2026-63952

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxc4f75bc8bd6b3d62665e1f5400c419540edb5601 < b3f4f82d1315f1439059a83d1c22c51a5b43d99eaffected
LinuxLinuxc4f75bc8bd6b3d62665e1f5400c419540edb5601 < 3be2a24f7f72ad7321ed6ad1715b956a4527bcf4affected
LinuxLinuxc4f75bc8bd6b3d62665e1f5400c419540edb5601 < 0995d1f79aed8ccbf62056189dd53fd19726ea08affected
LinuxLinuxc4f75bc8bd6b3d62665e1f5400c419540edb5601 < 555702282d4536a865dfffb1cd4f6028f196e7e8affected
LinuxLinuxc4f75bc8bd6b3d62665e1f5400c419540edb5601 < 3b041514cb6eae45869b020f743c14d983363222affected
LinuxLinux6.3affected
LinuxLinux0 < 6.3unaffected
LinuxLinux6.6.143 <= 6.6.*unaffected
LinuxLinux6.12.93 <= 6.12.*unaffected
LinuxLinux6.18.35 <= 6.18.*unaffected
LinuxLinux7.0.12 <= 7.0.*unaffected
LinuxLinux7.1 <= *unaffected

Weaknesses

References