CVE-2023-40548: Shim: interger overflow leads to heap buffer overflow in verify_sbat_section on 32-bits systems

Severity: high (CVSS 7.4 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 2026-06-26
Weakness: CWE-190

Description

A buffer overflow was found in Shim in the 32-bit system. The overflow happens due to an addition operation involving a user-controlled value parsed from the PE binary being used by Shim. This value is further used for memory allocation operations, leading to a heap-based buffer overflow. This flaw causes memory corruption and can lead to a crash or data integrity issues during the boot phase.

Affected products

Fedoraproject Fedora: 39
Red Hat Bootloader Team shim: before 15.8; 15.8-rc1 — 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

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