CVE-2026-8863
HIGH
Published Jun 9, 2026
Modified Jun 9, 2026
Description
Multiple Microsoft-sigend UEFI SHIM bootloaders are vulnerable to SecureBoot bypass. An attacker with administrative privileges or the ability to modify the boot process could use one of the vulnerable shim bootloaders to bypass Secure Boot protections and execute arbitrary code before the operating system loads. Specific UEFI DBX update is required to block these vulnerable boot loaders.
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CVSS v3.1 Score
7.8
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS — Exploit Prediction
0.0010
Probability of exploitation
0.01%
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
Frequently Asked Questions
What is CVE-2026-8863? +
Multiple Microsoft-sigend UEFI SHIM bootloaders are vulnerable to SecureBoot bypass. An attacker with administrative privileges or the ability to modify the boot process could use one of the vulnerable shim bootloaders to bypass Secure Boot protections and execute arbitrary code before the operating system loads. Specific UEFI DBX update is required to block these vulnerable boot loaders. It has a CVSS v3.1 base score of 7.8 (HIGH).
How severe is CVE-2026-8863? +
CVE-2026-8863 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0010, placing it in the 0th percentile for exploitation probability.
How do I check if I'm vulnerable to CVE-2026-8863? +
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.
