SEPTEMBER 17, 2026
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Case File

CVE-2026-54334

CRITICAL · CVSS 9.8 EPSS 0.43% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-09-14 · Last synced 2026-09-17

CyberRota Analysis

AI-Generated

The vulnerability affects UEFI firmware parsers, specifically in the handling of compressed firmware structures, allowing for heap memory corruption and potential arbitrary code execution due to improper index validation in the ReadCLen() function. This critical flaw, with a CVSS score of 9.8, poses significant risks for systems relying on UEFI firmware prior to version 1.14, making it essential for firmware developers and system integrators to prioritize patching to mitigate exploitation risks.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-54334
Severity
CRITICAL
CVSS
9.8
EPSS
0.43%

Original NVD Description

UEFI Firmware Parser parses BIOS, Intel ME, and UEFI firmware structures including volumes, file systems, and files. Prior to 1.14, ReadCLen() in uefi_firmware/compression/Tiano/Decompress.c reads Number from GetBits(Sd, CBIT) with CBIT = 9 and can obtain 511 entries for the 510-element Sd->mCLen heap array because its loop does not enforce Index < NC. The CharC == 2 run-length path can additionally request up to 531 zero writes through Sd->mCLen[Index++] = 0. The normal CompressedSection.process() to efi_compressor.TianoDecompress() to TianoDecompress() to DecodeC() to ReadCLen() parsing path therefore permits crafted Tiano or EFI compressed firmware to corrupt heap memory, deterministically crash the parsing process, and potentially execute code depending on build and runtime details. This issue is fixed in version 1.14.