CVE-2026-63952 (CVSS 8.4)

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.

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CVSS v3.1 Score

8.4

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

EPSS — Exploit Prediction

0.0016

Probability of exploitation

0.06%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

References

Other 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

Frequently Asked Questions

What is CVE-2026-63952? +

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. It has a CVSS v3.1 base score of 8.4 (HIGH).

How severe is CVE-2026-63952? +

CVE-2026-63952 has a CVSS v3.1 score of 8.4 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0016, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-63952? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

CVE-2026-63952