A divide‑by‑zero flaw exerts itself in the ext4_block_set_lb_size function of the lwext4 1.0.0 library. When a zero logical block size is encountered in a malformed ext4 image, the library triggers a floating‑point exception under sanitizers or crashes in standard builds, rendering the system or application unable to complete the mount or image processing operation. The vulnerability is a classic denial‑of‑service attack that destroys system availability without compromising confidentiality or integrity.

The vulnerability affects the lwext4 1.0.0 filesystem library. No vendor or product parent is listed, so any application directly linking against this library version is at risk. The flaw is present in the source file ext4_blockdev.c and has no known alternative library version that mitigates it.

The EPSS score is not available and the flaw is not listed in CISA KEV. With a CVSS score of 5.5, the vulnerability is assessed as medium severity, indicating a moderate risk to systems that rely on lwext4 when presented with a malformed ext4 image. The attack vector is inferred to be a crafted ext4 filesystem image supplied to a process that loads or mounts the image via the vulnerable library, which could originate from a malicious user or an untrusted input channel to the application. Successful exploitation would stop the victim program or service from completing the mount or image processing operation, resulting in a denial of service.