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TI-2026-39228 Aliases CVE-2026-54334GHSA-hm2w-vr2p-hq7w

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

Priority MEDIUM 50CWE-787Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-787 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00801 56th percentileScored 2026-11-07
Fix Fixed uefi-firmware-parser (theopolis): 1.14

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
theopolisuefi-firmware-parserbefore 1.141.14Patch availableCNA
—uefi-firmware (PyPI)up to 1.12—No fix listedGHSA-hm2w-vr2p-hq7w
  • uefi-firmware-parser Vendortheopolis Affected before 1.14 Fixed in 1.14 Patch available CNA
  • uefi-firmware (PyPI) Vendor— Affected up to 1.12 Fixed in — No fix listed GHSA-hm2w-vr2p-hq7w

Remediation

  • Fix · CNA uefi-firmware-parser (theopolis) Fixed in 1.14

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-54334
  2. 2026-10-03 Alias added: GHSA-hm2w-vr2p-hq7w

References

  • TI-2026-39227 UEFI Firmware Parser: Stack out-of-bounds write in tiano decompressor MakeTable CVSS 3.1CRITICAL 9.8

Sources