External risk intelligence

UEFI Firmware Parser Stack Corruption Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-54333

This vulnerability exists in a library designed for parsing local firmware files (BIOS, Intel ME, UEFI). It is a developer-oriented tool or build-time dependency used for static analysis or firmware manipulation, not a network service. It lacks typical public internet exposure as it is not intended to be deployed as an internet-facing gateway or endpoint.

Out-of-bounds Write

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability impacts a tool that parses firmware for systems like BIOS and UEFI. A flaw in how it handles compressed data could lead to system crashes or, in some scenarios, enable code execution. The main concern is determining if this tool is used within your environment and if so, whether it processes untrusted firmware files.

A parsing flaw can crash systems.
Understand if your firmware tools are affected.
Confirm relevance and exposure to this issue.

Attack Path

How an attacker could exploit the issue

An attacker could target the UEFI firmware parser with a specially crafted firmware file. If this file is processed by a vulnerable version of the parser, it can lead to a crash and potentially allow the attacker to execute their own code.

Requires attacker-controlled firmware file.
Vulnerable parser processes crafted input.
Risk of crashes and code execution.

Live Threat

Current exploitation, exposure, and threat context

When parsing crafted Tiano or EFI compressed firmware, the UEFI Firmware Parser could corrupt stack memory. This corruption may lead to a crash or potentially code execution, depending on system specifics.

BIOS, Intel ME, UEFI firmware structures.
Crafted firmware can corrupt stack memory.
Parsing process may crash or allow code execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in a UEFI firmware parsing library requires immediate attention from teams responsible for firmware analysis, development toolchains, or secure build environments. The first practical step is to identify all instances where this library is used, determine if these instances process untrusted firmware, and confirm ownership before planning remediation.

Firmware analysis or development toolchain owners.
Verify local or build-time usage of the parser.
Update to the patched version or isolate usage.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is UEFI Firmware Parser?

UEFI Firmware Parser is a utility library used by developers and security researchers to inspect, analyze, and manipulate low-level system firmware, including BIOS and Intel ME structures. It helps parse complex binary files like compressed volumes and file systems found in hardware firmware to understand their internal organization.

What does CWE-787 mean for CVE-2026-54333?

This CVE involves an out-of-bounds write, which is a memory safety flaw. In this case, the parser fails to check if values from a compressed firmware bitstream are within valid limits. This causes the software to overwrite adjacent memory, leading to stack corruption that can crash the program or potentially allow unauthorized code to run.

How is this vulnerability triggered?

The flaw is triggered when the library processes a maliciously crafted Tiano or EFI compressed firmware file. It will not be triggered by legitimate, well-formed firmware files, as the corruption only occurs when the input data intentionally provides invalid bit-length values that force the parser to write beyond its designated memory buffer.

Do I need to worry about internet exposure?

According to Halo Surface Signal, this is very unlikely to be an internet-facing risk. Because this is a developer tool used for offline static analysis or build-time processing, it is not typically deployed as a network service. You should primarily focus on systems where this library is integrated into local analysis pipelines.

What should I do to secure my environment?

Begin by identifying where the UEFI Firmware Parser is installed in your development or analysis environments. Once located, verify if these instances process untrusted or third-party firmware files. If usage is confirmed, update the library to version 1.14 or newer to incorporate the necessary input validation fixes.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.