CVE-2023-40547

HIGHNVD 8.38.3—
EchelonGraph scoreMEDIUM confidence

Score 8.3 from GitHub Security Advisory (severity: HIGH) published 2024-01-25. NVD baseline CVSS 8.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
8.3
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 5%CVSS: 8.3Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
8.3
EG Score
8.3(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: 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
Severity83% × 45%
Exploitation5% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
91.2%
KEV
Not listed

Published

January 25, 2024

Last Modified

June 26, 2026

Advisory Details (10)

Auto-updated Jun 26, 2026
Patch available. Sources: redhat.
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2023-40547
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.6 Extended

https://access.redhat.com/errata/RHSA-2024:2086
redhat Patch Available

Affected: Red Hat Enterprise Linux 7.

https://access.redhat.com/errata/RHSA-2024:1959
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2024:1903
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.

https://access.redhat.com/errata/RHSA-2024:1902
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.8 Extended

https://access.redhat.com/errata/RHSA-2024:1883
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.2 Extended Update Support.

https://access.redhat.com/errata/RHSA-2024:1876
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support, E4S Red Hat Enterprise Linux 8.4 Update Services for SA

https://access.redhat.com/errata/RHSA-2024:1873
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.0 Extended Update Support.

https://access.redhat.com/errata/RHSA-2024:1835
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.2 Advanced Update Support, Red Hat Enterprise Linux 8.2 Update Services for SAP Solutions, and Red

https://access.redhat.com/errata/RHSA-2024:1834

Vendor Advisories for CVE-2023-40547(9)

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

Patch Availability(9)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatshim-0:15.8-2.el8_62024-04-29redhat
redhatshim-signed-0:15.8-1.el72024-04-23redhat
redhatshim-0:15.8-2.el8_42024-04-18redhat
redhatshim-unsigned-x64-0:15.8-2.el82024-04-18redhat
redhatshim-0:15.8-4.el9_32024-04-18redhat
redhatshim-0:15.8-3.el9_22024-04-18redhat
redhatshim-0:15.8-4.el8_92024-04-18redhat
redhatshim-0:15.8-2.el8_22024-04-16redhat
redhatshim-unsigned-x64-0:15.8-2.el92024-04-16redhat

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.

Weakness Classification(3)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 12× in last 7d / 49× 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.

Showing the most recent 100 of 105 total refreshes for this CVE.

  1. 2026-07-23 02:25 UTCEG score recompute
  2. 2026-07-22 23:12 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2023-40547?
CVE-2023-40547 is a high vulnerability published on January 25, 2024. 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…
When was CVE-2023-40547 disclosed?
CVE-2023-40547 was first published in the National Vulnerability Database on January 25, 2024, with the most recent update on June 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2023-40547 actively exploited?
CVE-2023-40547 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 91.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2023-40547?
CVE-2023-40547 has a CVSS v3 base score of 8.3 (NVD).
How do I remediate CVE-2023-40547?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-40547, 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.

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