CVE-2023-5058

Code execution via unvalidated GIF LZW code size

Published Dec 7, 2023 · Updated Jul 28, 2025

Out-of-bounds write in Phoenix SecureCore Technology 4 allows local users to execute arbitrary code via a malicious GIF splash image. The SystemImageDecoderDxe DecodeLzwBytes routine uses an unvalidated GIF LZW CodeSize to index fixed 4,096-entry tables, causing writes beyond their bounds. Local privileged access to replace the protected splash image is required; successful exploitation runs in the DXE phase and can bypass Secure Boot or persist in firmware.

CVSS severity7.8
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Phoenix SecureCore Technology 4 allows local users to execute arbitrary code via a malicious GIF splash image. The SystemImageDecoderDxe DecodeLzwBytes routine uses an unvalidated GIF LZW CodeSize to index fixed 4,096-entry tables, causing writes beyond their bounds. Local privileged access to replace the protected splash image is required; successful exploitation runs in the DXE phase and can bypass Secure Boot or persist in firmware.

The record

CVE
CVE-2023-5058
Published
Dec 7, 2023
Updated
Jul 28, 2025
Vendor
Phoenix Technologies
Product
SecureCore Technology 4
Classifications
CWE-20, T1068, T1542.001
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Dec 7, 2023CVE publishedPublication date reported by the CVE source.
  2. Jul 28, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Phoenix Technologies · SecureCore Technology 4version=4.0

Published CVSS scores

8.2BinarlyCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1068Exploitation for Privilege Escalation
T1542.001Pre-OS Boot System Firmware

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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