--- id: CVE-2026-63952 title: 'memfd: deny writeable mappings when implying SEAL_WRITE' 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 m… severity: high cvss: 8.4 cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N' cvssSource: cna cwe: - CWE-266 vendor: Linux product: Linux affected: - >- Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < b3f4f82d1315f1439059a83d1c22c51a5b43d99e - >- Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < 3be2a24f7f72ad7321ed6ad1715b956a4527bcf4 - >- Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < 0995d1f79aed8ccbf62056189dd53fd19726ea08 - >- Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < 555702282d4536a865dfffb1cd4f6028f196e7e8 - >- Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < 3b041514cb6eae45869b020f743c14d983363222 - Linux 6.3 ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-10-16T15:34:10.687690Z' published: '2026-07-19' updated: '2026-10-19' sourceUpdated: '2026-10-19T20:17:59.011Z' source: CVEORG sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-63952' references: - url: 'https://git.kernel.org/stable/c/b3f4f82d1315f1439059a83d1c22c51a5b43d99e' - url: 'https://git.kernel.org/stable/c/3be2a24f7f72ad7321ed6ad1715b956a4527bcf4' - url: 'https://git.kernel.org/stable/c/0995d1f79aed8ccbf62056189dd53fd19726ea08' - url: 'https://git.kernel.org/stable/c/555702282d4536a865dfffb1cd4f6028f196e7e8' - url: 'https://git.kernel.org/stable/c/3b041514cb6eae45869b020f743c14d983363222' - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63952.json - url: 'https://access.redhat.com/security/cve/CVE-2026-63952' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2502422' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-63952' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63952' - url: >- https://lore.kernel.org/linux-cve-announce/2026071955-CVE-2026-63952-0c7b@gregkh/T - url: 'https://access.redhat.com/errata/RHSA-2026:69089' - url: 'https://access.redhat.com/errata/RHSA-2026:57251' - url: 'https://access.redhat.com/errata/RHSA-2026:67720' - url: 'https://access.redhat.com/errata/RHSA-2026:57252' tags: - cve.org - csaf - vex - red-hat epss: 0.00127 epssPercentile: 0.0239 patched: - enterprise_linux_appstream_eus_v_10_0 - enterprise_linux_appstream_v_10 - enterprise_linux_appstream_eus_v_9_6 - enterprise_linux_appstream_v_9 - enterprise_linux_baseos_eus_v_10_0 - enterprise_linux_baseos_v_10 - enterprise_linux_baseos_eus_v_9_6 - enterprise_linux_baseos_v_9 - enterprise_linux_codeready_linux_builder_eus_v_10_0 - enterprise_linux_codeready_linux_builder_v_10 - codeready_linux_builder_eus_v_9_6 - enterprise_linux_codeready_linux_builder_v_9 - enterprise_linux_real_time_for_nfv_eus_v_10_0 - enterprise_linux_real_time_for_nfv_v_10 - enterprise_linux_real_time_for_nfv_eus_v_9_6 - enterprise_linux_real_time_for_nfv_v_9 - enterprise_linux_real_time_eus_v_10_0 - enterprise_linux_real_time_v_10 - enterprise_linux_real_time_eus_v_9_6 - enterprise_linux_real_time_v_9 scores: cna: 8.4 vendor: 7 ingestedAt: '2026-10-16T17:24:46.784Z' --- ## Overview 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 - `Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < b3f4f82d1315f1439059a83d1c22c51a5b43d99e` - `Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < 3be2a24f7f72ad7321ed6ad1715b956a4527bcf4` - `Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < 0995d1f79aed8ccbf62056189dd53fd19726ea08` - `Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < 555702282d4536a865dfffb1cd4f6028f196e7e8` - `Linux >= c4f75bc8bd6b3d62665e1f5400c419540edb5601 < 3b041514cb6eae45869b020f743c14d983363222` - `Linux 6.3` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Vendor advisories - **RHSA-2026:69089** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux BaseOS EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0), Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0), Red Hat Enterprise Linux Real Time EUS (v. 10.0) · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69089) - **RHSA-2026:57251** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), Red Hat Enterprise Linux Real Time (v. 10) · released 2026-08-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:57251) - **RHSA-2026:67720** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6), Red Hat Enterprise Linux BaseOS EUS (v.9.6), Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6), Red Hat Enterprise Linux Real Time EUS (v.9.6) · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:67720) - **RHSA-2026:57252** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-08-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:57252) - **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 9 · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63952.json)