The vulnerability in barebox's EFI PE loader (efi/loader/pe.c) arises from an integer overflow in 32-bit arithmetic when computing virtual image size using section VirtualAddress and size values. This causes undersized heap allocation. Additionally, the PE section loading logic does not properly validate that PointerToRawData plus the copied size remains within the PE file buffer, enabling heap buffer overflow or out-of-bounds heap reads. An attacker can exploit this by providing a crafted EFI PE binary through various boot methods (TFTP, USB, SD card, network boot), potentially achieving arbitrary code execution in the bootloader environment. The vulnerability is tracked as CVE-2026-34963 and classified under CWE-190 (Integer Overflow or Wraparound).

Successful exploitation can lead to heap buffer overflow or out-of-bounds memory reads in the bootloader, which may result in arbitrary code execution with bootloader privileges. This compromises the boot process integrity and can allow attackers to execute malicious code early in system startup.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided at this time. Until a patch is available, avoid loading untrusted EFI PE binaries from external sources such as TFTP, USB, SD card, or network boot to reduce exposure.