CVE-2026-63952
Kernel memfd seal bug allows writable mappings despite SEAL_WRITE.
Is CVE-2026-63952 being exploited?
Not confirmed. CVE-2026-63952 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.16% probability of exploitation in the next 30 days.
How severe is CVE-2026-63952?
CVE-2026-63952 is rated High with a CVSS score of 8.4. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-63952?
Yes. A fix has been recorded for CVE-2026-63952. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-63952 affect?
CVE-2026-63952 affects Linux kernel (memfd seals: memfd_create / seals). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-63952?
Apply vendor kernel updates; restrict untrusted local access until patched.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Local attacker can use SEAL_EXEC to bypass SEAL_WRITE, modify supposedly write-sealed memfd and tamper code/data, enabling sandbox escape or code injection.
Patch when possible
- affected>= c4f75bc8bd6b3d62665e1f5400c419540edb5601 and < b3f4f82d1315f1439059a83d1c22c51a5b43d99e
- affected>= c4f75bc8bd6b3d62665e1f5400c419540edb5601 and < 3be2a24f7f72ad7321ed6ad1715b956a4527bcf4
- affected>= c4f75bc8bd6b3d62665e1f5400c419540edb5601 and < 0995d1f79aed8ccbf62056189dd53fd19726ea08
- affected>= c4f75bc8bd6b3d62665e1f5400c419540edb5601 and < 555702282d4536a865dfffb1cd4f6028f196e7e8
- affected>= c4f75bc8bd6b3d62665e1f5400c419540edb5601 and < 3b041514cb6eae45869b020f743c14d983363222
- affected6.3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.