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No exploitation reportedFix available

CVE-2023-40547

No exploitation reported by the sources we read.

  • Published2024-01-25
  • WeaknessCWE-346 · CWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A remote code execution vulnerability was found in Shim. The Shim boot support trusts attacker-controlled values when parsing an HTTP response. This flaw allows an attacker to craft a specific malicious HTTP request, leading to a completely controlled out-of-bounds write primitive and complete system compromise. This flaw is only exploitable during the early boot phase, an attacker needs to perform a Man-in-the-Middle or compromise the boot server to be able to exploit this vulnerability successfully.

Timeline

dates in UTC
  1. 2024-01-2516:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2023-40547?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2023-40547?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Redhat enterprise linux
BranchAffectedFixed in
7.0= 7.0no fix published
8.0= 8.0no fix published
9.0= 9.0no fix published
Redhat shim
BranchAffectedFixed in
15.8< 15.815.8

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionnone2024-02-13
  • OpenCVESSVC decisionnone—
  • CNACVSS 3.18.3read 2026-10-23
  • NVDCVSS 3.18.3read 2026-10-23
  • CNAweakness (CWE)CWE-787read 2026-10-23
  • NVDweakness (CWE)CWE-346, CWE-787read 2026-10-23
  • FIRST EPSSEPSS score5.4 %2026-10-22

Technical details

CVSS v3 Vector
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Published
2024-01-25
Last Modified
2026-06-26
NVD status
Modified

Frequently asked questions

What is CVE-2023-40547?

A remote code execution vulnerability was found in Shim. The Shim boot support trusts attacker-controlled values when parsing an HTTP response. This flaw allows an attacker to craft a specific malicious HTTP request, leading to a completely controlled out-of-bounds write primitive and complete system compromise. This flaw is only exploitable during the early boot phase, an attacker needs to perform a Man-in-the-Middle or compromise the boot server to be able to exploit this vulnerability successfully.

Is CVE-2023-40547 actively exploited?

Active exploitation of CVE-2023-40547 has not been confirmed. Its EPSS score was 5.4% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2023-40547?

CVE-2023-40547 has a CVSS v3 base score of 8.3 (HIGH severity), with vector string CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H.

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