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CVE-2026-8863 is a UEFI Secure Boot security feature bypass affecting multiple legacy Microsoft-signed shim bootloaders, primarily shim version 0.9 and earlier. On UEFI-based systems that trust the Microsoft Corporation UEFI CA 2011 third-party certificate, these old shim binaries remain accepted as valid first-stage bootloaders and can be introduced by an attacker even if the original software package is not installed on the target. The weakness allows an attacker to use an outdated but still-trusted shim to transfer trust to vulnerable or revoked second-stage boot components, especially GRUB 2, or to bypass newer boot-chain protections absent from legacy shim generations, including Machine Owner Key denylist enforcement and Secure Boot Advanced Targeting checks. As a result, Secure Boot can be defeated without requiring a memory-corruption exploit, enabling execution of untrusted code in the pre-OS boot chain.
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No valid public exploits. Mallory filtered out 1 candidate as fakes, detection scripts, or README-only repos.
All candidate exploits were filtered out by Mallory's validation.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
21 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Secure Boot bypass vulnerability affecting old Microsoft-signed UEFI shim bootloaders, allowing execution of untrusted code during boot on systems that trust the Microsoft third-party UEFI certificate.
A vulnerability designation associated with old and forgotten Linux UEFI shim bootloaders (versions 0.9 and below) that can be abused to bypass UEFI Secure Boot on systems trusting Microsoft's third-party UEFI CA, enabling execution of untrusted code during boot and deployment of malicious UEFI bootkits.
A vulnerability designation covering Microsoft-signed vulnerable UEFI shim bootloaders that can be abused to bypass UEFI Secure Boot and load untrusted code during boot.
A vulnerability in old Microsoft-signed UEFI shim bootloaders that allows attackers to bypass UEFI Secure Boot by bringing their own vulnerable shim and executing untrusted code during boot.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.