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CVE-2026-10797 is a legacy flaw in the open-source UEFI shim bootloader, affecting shim version 0.9 and earlier, that can undermine UEFI Secure Boot revocation enforcement. The issue arises from inconsistent parsing of Authenticode signature metadata in PE binaries: shim uses one signature-length field during revocation checking and a different structure during signature verification. Because an Authenticode-signed PE image stores signature length information in two locations, an attacker can tamper with the second-stage bootloader’s WIN_CERTIFICATE header so that shim’s certificate-based revocation logic examines incorrect or bogus signature data while normal signature verification still succeeds against the actual embedded signature. As a result, certificate-based denylist checks using dbx or MokListX can be bypassed for a second-stage bootloader that would otherwise be revoked. The flaw was fixed upstream years earlier, but older Microsoft-signed shim binaries carrying the bug remained trusted on many systems until later revocation actions.
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A revocation-check flaw in old UEFI shim bootloaders where the shim reads signature size from the wrong PE structure, allowing attackers to bypass dbx/MokListX revocation checks.
A Secure Boot revocation bypass in old signed shims caused by inconsistent parsing of PE signature length fields during revocation checking versus signature verification, allowing certificate-based revocations in dbx or MokListX to be bypassed by tampering with the WIN_CERTIFICATE structure of a second-stage loader.
A shim vulnerability in version 0.9 and below caused by inconsistent trust in PE signature length fields, enabling bypass of certificate-based revocation checks for second-stage bootloaders.
A shim vulnerability that allowed the certificate-based revocation mechanism to be bypassed by modifying the second-stage bootloader's signature header.
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.