CVE-2026-54334: CWE-787: Out-of-bounds Write in theopolis uefi-firmware-parser
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.
AI Analysis
Technical Summary
The vulnerability exists in the ReadCLen() function of the uefi-firmware-parser component of theopolis project. Specifically, the function reads a number of entries from a bitstream without properly enforcing the upper bound on the index, allowing up to 511 entries to be written into a 510-element heap array (Sd->mCLen). Additionally, a run-length encoding path can request up to 531 zero writes, further exceeding the array bounds. This out-of-bounds write can corrupt heap memory, cause deterministic crashes during firmware parsing, and potentially enable code execution depending on the environment. The flaw affects versions prior to 1.14 and is resolved in 1.14.
Potential Impact
Successful exploitation can lead to heap memory corruption, causing the firmware parsing process to crash deterministically. Depending on build and runtime details, it may also allow an attacker to execute arbitrary code. The vulnerability has a CVSS 3.1 score of 9.8, indicating critical severity with high impact on confidentiality, integrity, and availability.
Mitigation Recommendations
Upgrade to version 1.14 or later of theopolis uefi-firmware-parser, where this vulnerability is fixed. No other mitigations are specified. Patch status is confirmed fixed in 1.14.
CVE-2026-54334: CWE-787: Out-of-bounds Write in theopolis uefi-firmware-parser
Description
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.
CVSS v3.1
Score 9.8critical
Affected software
theopolis
uefi-firmware-parser
pkg:github/theopolis/uefi-firmware-parserRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability exists in the ReadCLen() function of the uefi-firmware-parser component of theopolis project. Specifically, the function reads a number of entries from a bitstream without properly enforcing the upper bound on the index, allowing up to 511 entries to be written into a 510-element heap array (Sd->mCLen). Additionally, a run-length encoding path can request up to 531 zero writes, further exceeding the array bounds. This out-of-bounds write can corrupt heap memory, cause deterministic crashes during firmware parsing, and potentially enable code execution depending on the environment. The flaw affects versions prior to 1.14 and is resolved in 1.14.
Potential Impact
Successful exploitation can lead to heap memory corruption, causing the firmware parsing process to crash deterministically. Depending on build and runtime details, it may also allow an attacker to execute arbitrary code. The vulnerability has a CVSS 3.1 score of 9.8, indicating critical severity with high impact on confidentiality, integrity, and availability.
Mitigation Recommendations
Upgrade to version 1.14 or later of theopolis uefi-firmware-parser, where this vulnerability is fixed. No other mitigations are specified. Patch status is confirmed fixed in 1.14.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-12T19:23:22.316Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6aa8567355bf5e2cf58d7f05
Added to database: 09/14/2026, 20:17:55 UTC
Last enriched: 09/14/2026, 20:31:47 UTC
Last updated: 09/15/2026, 03:08:01 UTC
Views: 8
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