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TI-2026-39227 Aliases CVE-2026-54333GHSA-2689-5p89-6j3j

UEFI Firmware Parser: Stack out-of-bounds write in tiano decompressor MakeTable

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, MakeTable() in uefi_firmware/compression/Tiano/Decompress.c does not validate that bit-length values read from a crafted Tiano or EFI compressed firmware bitstream remain within the expected range from 0 through 16. The normal CompressedSection.process() to efi_compressor.TianoDecompress() to TianoDecompress() to ReadPTLen() to MakeTable() parsing path can consequently write beyond the stack-allocated Count[17] array and related decode tables. The resulting stack corruption deterministically crashes the parsing process and may permit code execution 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-2689-5p89-6j3j
  • 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-2689-5p89-6j3j

Remediation

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

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-54333
  2. 2026-10-03 Alias added: GHSA-2689-5p89-6j3j

References

Other 5

  • TI-2026-39228 UEFI Firmware Parser: Heap out-of-bounds write in tiano decompressor `ReadCLen` CVSS 3.1CRITICAL 9.8

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences