PT-2026-56683 · Pypi · Uefi Firmware

CVE-2026-54333 · Published 2026-04-16 · Updated 2026-07-13

OSV

CVSS v3.1

9.8

Critical

Base vector

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

uefi-firmware contains a stack out-of-bounds write vulnerability in the native tiano/EFI decompressor. in uefi firmware/compression/Tiano/Decompress.c, MakeTable() does not validate that bit-length values read from the compressed bitstream are within the expected range (0..16). a crafted firmware blob can supply bit lengths greater than 16, causing out-of-bounds writes to the stack-allocated Count[17] array and related decode tables.

reachability is through the normal parsing path: CompressedSection.process() -> efi compressor.TianoDecompress() -> TianoDecompress() -> ReadPTLen() -> MakeTable().

Minimum impact is a deterministic crash; depending on build/runtime details, the stack 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.

References:

• PR: https://github.com/theopolis/uefi-firmware-parser/pull/145
• fix commit: https://github.com/theopolis/uefi-firmware-parser/commit/bf3dfaa8a05675bae6ea0cbfa082ddcebfcde23e
• upstream related fixes: CVE-2017-5731, CVE-2017-5732, CVE-2017-5733, CVE-2017-5734, CVE-2017-5735

Fix

Memory Corruption

Weakness Enumeration

CWE-787

Related Identifiers

CVE-2026-54333

GHSA-2689-5P89-6J3J

PYSEC-2026-3393

Affected Products

Uefi Firmware

References · 9

• https://osv.dev/vulnerability/GHSA-2689-5p89-6j3j · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-54333 · Security Note
• https://osv.dev/vulnerability/PYSEC-2026-3393 · Vendor Advisory
• https://github.com/theopolis/uefi-firmware-parser · Note
• https://github.com/theopolis/uefi-firmware-parser/security/advisories/GHSA-2689-5p89-6j3j · Note
• https://github.com/theopolis/uefi-firmware-parser/pull/145 · Note
• https://github.com/theopolis/uefi-firmware-parser/commit/bf3dfaa8a05675bae6ea0cbfa082ddcebfcde23e · Note
• https://github.com/advisories/GHSA-2689-5p89-6j3j · Note
• https://pypi.org/project/uefi-firmware · Note