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Mallory
Medium

Eurosoft Boot Loader Bypass

IdentifiersCVE-2022-34303CWE-693

A flaw was found in Eurosoft UEFI bootloaders before 2022-06-01 that allows Secure Boot protections to be bypassed. The vulnerable bootloader is signed and therefore trusted by Secure Boot, but it can be abused to load and execute arbitrary code during the pre-boot phase. An attacker can replace the legitimate signed bootloader in use with the vulnerable Eurosoft bootloader and then use it to tamper with or bypass Secure Boot enforcement. This is a pre-OS trust-chain failure affecting the integrity of the boot process rather than a conventional operating-system-level memory corruption issue.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows an attacker to defeat Secure Boot protections and execute arbitrary code before the operating system loads. This undermines the integrity of the platform boot chain and can enable deployment of bootkits or other pre-boot malware, tampering with firmware/boot components, persistence across reboots, and evasion of OS-level security controls that rely on a trustworthy boot state.

Mitigation

If you can’t patch tonight, do this now.

Restrict write access to the EFI System Partition and prevent unauthorized bootloader replacement. Limit or disable booting from external media where operationally feasible, protect firmware settings with strong BIOS/UEFI passwords, and monitor for unauthorized changes to boot components. Deploy Secure Boot DBX revocation updates promptly, verify BitLocker and servicing stack prerequisites where relevant for KB5012170 deployment, and consider stronger platform controls such as custom Secure Boot keys in high-assurance environments.

Remediation

Patch, then assume compromise.

Apply vendor and platform updates that revoke the vulnerable bootloader through Secure Boot DBX updates. Microsoft associated this issue with security update KB5012170, which updates the Secure Boot forbidden signature database (DBX) on supported Windows platforms to block vulnerable third-party UEFI bootloaders. Replace any affected Eurosoft bootloaders with fixed versions released after 2022-06-01 or other non-vulnerable boot components, and ensure revocation updates are successfully deployed across the fleet.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
EurosoftUefi Bootloaderoperating_system
Microsoft CorporationWindows 10operating_system
Microsoft CorporationWindows 11operating_system
Microsoft CorporationWindows 8.1operating_system
Microsoft CorporationWindows Rt 8.1operating_system
Microsoft CorporationWindows Server 2012operating_system
Microsoft CorporationWindows Server 2016operating_system
Microsoft CorporationWindows Server 2019operating_system
Microsoft CorporationWindows Server 2022operating_system
New Horizon Datasys Inc.Unknown Bootloaderapplication
Red HatEnterprise Linuxoperating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity

Community discussion across Reddit, Mastodon, and other social sources.