CVE-2026-63952
memfd: deny writeable mappings when implying SEAL_WRITE
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.
INFO
Published Date :
July 19, 2026, 4:17 p.m.
Last Modified :
July 27, 2026, 5:44 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
Solution
- Update the Linux kernel.
- Apply the security patch.
- Ensure implied seals are set correctly.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-63952.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-63952 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-63952
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-63952 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-63952 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 20, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N -
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 19, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'c4f75bc8bd6b3d62665e1f5400c419540edb5601', 'lessThan': 'b3f4f82d1315f1439059a83d1c22c51a5b43d99e', 'versionType': 'git'}, {'status': 'affected', 'version': 'c4f75bc8bd6b3d62665e1f5400c419540edb5601', 'lessThan': '3be2a24f7f72ad7321ed6ad1715b956a4527bcf4', 'versionType': 'git'}, {'status': 'affected', 'version': 'c4f75bc8bd6b3d62665e1f5400c419540edb5601', 'lessThan': '0995d1f79aed8ccbf62056189dd53fd19726ea08', 'versionType': 'git'}, {'status': 'affected', 'version': 'c4f75bc8bd6b3d62665e1f5400c419540edb5601', 'lessThan': '555702282d4536a865dfffb1cd4f6028f196e7e8', 'versionType': 'git'}, {'status': 'affected', 'version': 'c4f75bc8bd6b3d62665e1f5400c419540edb5601', 'lessThan': '3b041514cb6eae45869b020f743c14d983363222', 'versionType': 'git'}], 'programFiles': ['mm/memfd.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.3'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.3', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.6.143', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.93', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.35', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.0.12', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['mm/memfd.c'], 'defaultStatus': 'affected'}] Added 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. Added Reference https://git.kernel.org/stable/c/0995d1f79aed8ccbf62056189dd53fd19726ea08 Added Reference https://git.kernel.org/stable/c/3b041514cb6eae45869b020f743c14d983363222 Added Reference https://git.kernel.org/stable/c/3be2a24f7f72ad7321ed6ad1715b956a4527bcf4 Added Reference https://git.kernel.org/stable/c/555702282d4536a865dfffb1cd4f6028f196e7e8 Added Reference https://git.kernel.org/stable/c/b3f4f82d1315f1439059a83d1c22c51a5b43d99e