--- title: Schneier on Security | daily.dev description: ESET researchers discovered that Microsoft's Secure Boot has been trivially bypassable for 13 of its 14 years of existence. The flaw stems from Microsoft's... canonical: https://daily.dev/posts/schneier-on-security-gtentyiez twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Schneier on Security | daily.dev og:description: ESET researchers discovered that Microsoft's Secure Boot has been trivially bypassable for 13 of its 14 years of existence. The flaw stems from Microsoft's... og:url: https://daily.dev/posts/schneier-on-security-gtentyiez og:image: https://api.daily.dev/og/posts/GtENTYiEz.png og:image:alt: Schneier on Security og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Schneier on Security **[Schneier on Security](https://daily.dev/sources/schneier)** · 1 min read · 2 upvotes · 0 comments ## Summary ESET researchers discovered that Microsoft's Secure Boot has been trivially bypassable for 13 of its 14 years of existence. The flaw stems from Microsoft's failure to revoke 11 known-defective firmware shim images — some dating back to 2013 — that remained signed and publicly available. These shims, originally created to extend Secure Boot to Linux devices, can be exploited by even novice attackers to completely circumvent UEFI-level firmware protection. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why is Microsoft Secure Boot vulnerable to bypass even though it's supposed to prevent firmware infections? Microsoft failed to revoke 11 publicly available shim images that were known to be defective, including at least one dating to 2013. Shims extend Secure Boot to Linux devices and utility software, and because Microsoft signs and oversees them, the unrevoked defective shims let attackers bypass UEFI-embedded Secure Boot protections using a technique simple enough for novice hackers. _Teams hardening boot security can track firmware and Secure Boot disclosures like this one on daily.dev._ ### What are shims in the context of Secure Boot and why do they matter for security? Shims are signed firmware images created to extend Microsoft's Secure Boot to Linux devices and utility software that Microsoft doesn't natively support. Because Microsoft controls shim signing, a defective or outdated shim that remains signed and unrevoked can be exploited to completely circumvent Secure Boot's UEFI-level protection against firmware infections. _Anyone auditing UEFI trust chains can follow firmware vulnerability findings like this via daily.dev._ ## Similar posts on daily.dev - [Windows and Linux users: The deadline to update Secure Boot keys is near](https://daily.dev/posts/windows-and-linux-users-the-deadline-to-update-secure-boot-keys-is-near-nvkg8wx89) · Ars Technica · 35 upvotes · 2 comments - [Exploiting signed bootloaders to circumvent UEFI Secure Boot](https://daily.dev/posts/exploiting-signed-bootloaders-to-circumvent-uefi-secure-boot-ardovrgf9) · Hacker News · 0 upvotes · 0 comments - [I always disable this one feature in every UEFI / BIOS](https://daily.dev/posts/i-always-disable-this-one-feature-in-every-uefi-bios-fke837jjx) · XDA Developers · 1 upvotes · 0 comments - [What you need to know about the Microsoft Secure Boot certificate expiration: Don’t Panic\!](https://daily.dev/posts/what-you-need-to-know-about-the-microsoft-secure-boot-certificate-expiration-don-t-panic--fm8qejjsl) · Fedora Magazine · 0 upvotes · 0 comments --- Tags: [#security](https://daily.dev/tags/security), [#microsoft](https://daily.dev/tags/microsoft), [#vulnerability](https://daily.dev/tags/vulnerability), [#firmware](https://daily.dev/tags/firmware) [View this post on daily.dev](https://daily.dev/posts/schneier-on-security-gtentyiez) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Schneier on Security","url":"https://daily.dev/posts/schneier-on-security-gtentyiez","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/schneier-on-security-gtentyiez"},"datePublished":"2026-07-29T11:06:35.385Z","dateModified":"2026-09-13T18:53:23.190Z","description":"ESET researchers discovered that Microsoft's Secure Boot has been trivially bypassable for 13 of its 14 years of existence. 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Shims extend Secure Boot to Linux devices and utility software, and because Microsoft signs and oversees them, the unrevoked defective shims let attackers bypass UEFI-embedded Secure Boot protections using a technique simple enough for novice hackers. Teams hardening boot security can track firmware and Secure Boot disclosures like this one on daily.dev."}},{"@type":"Question","name":"What are shims in the context of Secure Boot and why do they matter for security?","acceptedAnswer":{"@type":"Answer","text":"Shims are signed firmware images created to extend Microsoft's Secure Boot to Linux devices and utility software that Microsoft doesn't natively support. Because Microsoft controls shim signing, a defective or outdated shim that remains signed and unrevoked can be exploited to completely circumvent Secure Boot's UEFI-level protection against firmware infections. Anyone auditing UEFI trust chains can follow firmware vulnerability findings like this via daily.dev."}}]} ```