VYPR
Unrated severityNVD Advisory· Published Jan 29, 2024· Updated Nov 20, 2025

Shim: out-of-bounds read in verify_buffer_authenticode() malformed pe file

CVE-2023-40549

Description

An out-of-bounds read in Shim's PE loader allows a crafted binary to crash the boot loader, causing denial of service.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

An out-of-bounds read in Shim's PE loader allows a crafted binary to crash the boot loader, causing denial of service.

Vulnerability

An out-of-bounds read flaw exists in Shim due to insufficient boundary verification when loading a PE binary [2]. This affects Shim versions prior to the fixes included in Red Hat Enterprise Linux updates [1][4]. The vulnerability is triggered during the parsing of a maliciously crafted PE file.

Exploitation

An attacker with the ability to provide a crafted PE binary to the Shim boot loader (e.g., via a malicious boot image or during the boot process) can trigger the out-of-bounds read. No authentication is required, but the attacker must have a means to load the crafted binary in a Secure Boot environment.

Impact

Successful exploitation causes Shim to read beyond the allocated buffer, leading to a crash and denial of service. The impact is limited to availability; no code execution or privilege escalation is indicated.

Mitigation

Red Hat has released updates for Shim as part of RHSA-2024:1903, RHSA-2024:1959, and RHSA-2024:2086 [1][3][4]. Users should apply the latest Shim package for their respective Red Hat Enterprise Linux versions. No workaround is available; updating is the recommended mitigation.

AI Insight generated on May 25, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

39

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

11

News mentions

0

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