CVE-2023-40551: Shim: out of bounds read when parsing mz binaries

Severity: medium (CVSS 5.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-01-29 · updated 2026-06-17
Weakness: CWE-125

Description

A flaw was found in the MZ binary format in Shim. An out-of-bounds read may occur, leading to a crash or possible exposure of sensitive data during the system's boot phase.

Affected products

Fedoraproject Fedora: 39
Red Hat Enterprise Linux: 8.0, 9.0
Red Hat Bootloader Team shim: before 15.8 — fixed in 15.8

How to fix

Upgrade to a fixed version: Red Hat Bootloader Team shim 15.8. Check the vendor advisory for mitigations.

References

https://access.redhat.com/errata/RHSA-2024:1834
https://access.redhat.com/errata/RHSA-2024:1835
https://access.redhat.com/errata/RHSA-2024:1873
https://access.redhat.com/errata/RHSA-2024:1876
https://access.redhat.com/errata/RHSA-2024:1883
https://access.redhat.com/errata/RHSA-2024:1902
https://access.redhat.com/errata/RHSA-2024:1903
https://access.redhat.com/errata/RHSA-2024:1959
https://access.redhat.com/errata/RHSA-2024:2086
https://access.redhat.com/security/cve/CVE-2023-40551
https://bugzilla.redhat.com/show_bug.cgi?id=2259918
https://access.redhat.com/errata/RHSA-2024:1834

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