PT-2026-56684 · Pypi · Uefi Firmware

CVE-2026-54334

Published

2026-04-16

Updated

2026-07-13

CVSS v3.1

9.8

Critical

Vector

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

uefi-firmware contains a heap out-of-bounds write vulnerability in the native tiano/EFI decompressor. in uefi firmware/compression/Tiano/Decompress.c, ReadCLen() reads Number = GetBits(Sd, CBIT) with CBIT = 9, so Number can be as large as 511, while the destination array Sd->mCLen has NC = 510 elements. the loop writes while Index < Number without enforcing Index < NC. additionally, the CharC == 2 run-length path performs GetBits(Sd, 9) + 20, allowing up to 531 zero writes through Sd->mCLen[Index++] = 0.

Reachability is through the normal parsing path: CompressedSection.process() -> efi compressor.TianoDecompress() -> TianoDecompress() -> DecodeC() -> ReadCLen().

Minimum impact is a deterministic crash; depending on build/runtime details, the heap memory corruption may be exploitable for code execution in the context of the parsing process. this project shipped its own copy of the decompressor without the upstream EDK2 hardening for this bug class.