GHSA-HM2W-VR2P-HQ7W

uefi-firmware contains a heap out-of-bounds write vulnerability in the native tiano/EFI decompressor. in uefi_firmware/compression/Tiano/Decompress.c, ReadCLen() reads Number = GetBits(Sd, CBIT) with CBIT = 9, so Number can be as large as 511, while the destination array Sd->mCLen has NC = 510 elements. the loop writes while Index < Number without enforcing Index < NC. additionally, the CharC == 2 run-length path performs GetBits(Sd, 9) + 20, allowing up to 531 zero writes through Sd->mCLen[Index++] = 0.

Reachability is through the normal parsing path: CompressedSection.process() -> efi_compressor.TianoDecompress() -> TianoDecompress() -> DecodeC() -> ReadCLen().

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

• 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

A write operation targets a memory location beyond the intended buffer boundary. Typical impact: memory corruption, crash, or arbitrary code execution.

GHSA-HM2W-VR2P-HQ7W has a CVSS score of 9.8 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

1. What is GHSA-HM2W-VR2P-HQ7W? GHSA-HM2W-VR2P-HQ7W is a critical-severity out-of-bounds write vulnerability in uefi-firmware (pip), affecting versions <= 1.12. No fixed version is listed yet. A write operation targets a memory location beyond the intended buffer boundary.
2. How severe is GHSA-HM2W-VR2P-HQ7W? GHSA-HM2W-VR2P-HQ7W has a CVSS score of 9.8 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of uefi-firmware are affected by GHSA-HM2W-VR2P-HQ7W? uefi-firmware (pip) versions <= 1.12 is affected.
4. Is there a fix for GHSA-HM2W-VR2P-HQ7W? No fixed version is listed for GHSA-HM2W-VR2P-HQ7W yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is GHSA-HM2W-VR2P-HQ7W exploitable, and should I be worried? Whether GHSA-HM2W-VR2P-HQ7W is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-HM2W-VR2P-HQ7W is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-HM2W-VR2P-HQ7W? No fixed version is listed yet. In the interim: Keep the dependency up to date. In native-code projects, use bounds-checked containers and enable compiler hardening flags.