An out-of-bounds read occurs in the ext4_ext_binsearch_idx function of the lwext4 1.0.0 library when parsing an ext4 filesystem image. The flaw stems from insufficient validation of extent header fields before performing a binary search over extent index entries, resulting in invalid pointer calculations and a memory read outside the extent tree bounds. The erroneous read can crash the library, causing any dependent application to stop functioning and leading to a denial‑of‑service scenario without granting remote code execution.

The vulnerable component is the lwext4 lightweight ext4 implementation, version 1.0.0, which is used by embedded and specialized systems that rely on external ext4 images. Although no vendor is listed in the CNA data, any deployment that incorporates the open‑source library and accepts untrusted filesystem images is potentially exposed.

Exploitation requires an attacker to supply a crafted ext4 filesystem image in which the extent header fields contain values that trigger the out-of-bounds read. Once the library processes the file, it is likely to crash, halting services that depend on the filesystem parser. There is no privilege escalation or remote code execution, but the impact on availability can be significant. The EPSS score is not available and the vulnerability is not listed in CISA KEV, indicating that no widely documented exploitation has been reported. The CVSS score of 6.5 reflects a moderate severity, and the lack of known exploitation suggests an uncertain but non‑negligible likelihood of attack in environments where untrusted images are processed.