CVE-2026-54334

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-04-16. the CNA's CVSS baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:github_m, ghsa
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: —CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

UEFI Firmware Parser has a heap out-of-bounds write in tiano decompressor ReadCLen

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:
  • fix commit:
  • upstream related fixes: CVE-2017-5731, CVE-2017-5732, CVE-2017-5733, CVE-2017-5734, CVE-2017-5735

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
—
KEV
Not listed

Published

April 16, 2026

Last Modified

April 16, 2026

Vendor Advisories for CVE-2026-54334(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
pipuefi-firmware—ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
uefi-firmware1.1 ... 1.9 (10 versions)——

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 1× in last 7d / 3× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-23 03:19 UTCEG score recompute
  2. 2026-07-08 17:45 UTCEG score recompute
  3. 2026-07-08 17:45 UTCGHSA enrichment

Frequently asked(4)

What is CVE-2026-54334?
CVE-2026-54334 is a critical vulnerability published on April 16, 2026. UEFI Firmware Parser has a heap out-of-bounds write in tiano decompressor ReadCLen 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…
When was CVE-2026-54334 disclosed?
CVE-2026-54334 was first published in the National Vulnerability Database on April 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-54334?
CVE-2026-54334 has a CVSS v4.0 base score of 9.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-54334?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54334, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-54334

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