barebox versions prior to 2026.04.0 contain out-of-bounds read vulnerabilities in the ext4 filesystem extent parsing code. The issue arises from missing validation of the eh_entries field against buffer capacity, which can lead to heap out-of-bounds reads during boot-time filesystem parsing. An attacker can exploit this by supplying a malicious ext4 filesystem image via USB, SD card, or network boot. This vulnerability has been assigned CVE-2026-34961 and is rated medium severity. A patch is available in version 2026.04.0.