UEFI Firmware Parser: Heap out-of-bounds write in tiano decompressor `ReadCLen`

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-54334
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-14 20:16:46 UTC
Updated2026-09-30 17:51:56 UTC
DescriptionUEFI 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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.008010000 probability, percentile 0.549050000 (date 2026-09-29)

Problem Types: CWE-787 | CWE-787 CWE-787: Out-of-bounds Write

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Theopolis Uefi-firmware-parser affected < 1.14 Not specified

References

ReferenceSourceLinkTags
github.com/theopolis/uefi-firmware-parser/releases/tag/v1.14 [email protected] github.com
github.com/theopolis/uefi-firmware-parser/commit/bf3dfaa8a05675bae6ea0cb... [email protected] github.com
github.com/theopolis/uefi-firmware-parser/pull/145 [email protected] github.com
github.com/theopolis/uefi-firmware-parser/security/advisories/GHSA-hm2w-... [email protected] github.com
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