# CVE-2025-70099: lwext4 NULL pointer dereference in ext4_dir_en_get_name_len

Source: https://junglewise.ai/threats/cve-2025-70099-lwext4-null-pointer-dereference-in-ext4-dir-en-get-name-len  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-01. Updated: 2026-06-01  
License: CC BY 4.0 with a link back

CVE-2025-70099 · Severity: info · CVSS 0 · Published 2026-06-01

lwext4 is a lightweight library used to provide EXT4 filesystem support for embedded systems and small devices. A vulnerability in how the library handles directory information could allow a malicious actor to crash a system by providing a specially crafted, corrupted filesystem image. This results in a denial of service, potentially causing devices to reboot or stop functioning when they attempt to read the malicious data.

Technologies: [Grzegorz Kostka Lwext4](https://junglewise.ai/threats/technologies/lwext4). Vendors: [Grzegorz Kostka](https://junglewise.ai/threats/vendors/grzegorz-kostka).

## Quick answers

**Is CVE-2025-70099 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-70099 being exploited in the wild.

**How severe is CVE-2025-70099?** Informational severity, with a CVSS score of 0, published 1 June 2026.

**Which products and versions are affected?** Grzegorz Kostka Lwext4 1.0.0.

**Is there a fix for CVE-2025-70099?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2025-70099 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2025-70099?** Check whether you run Grzegorz Kostka Lwext4 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A NULL pointer dereference exists in the ext4_dir_en_get_name_len function within include/ext4_dir.h of lwext4 1.0.0. The vulnerability is triggered during directory iteration when the library processes a malformed EXT4 filesystem image containing corrupted directory entries. Specifically, the ext4_dir_entry_next function may pass an invalid or NULL directory entry pointer to ext4_dir_en_get_name_len, which attempts to access the name_len field without prior validation. This results in a segmentation fault and subsequent denial of service. The issue was identified via fuzzing and affects the 2016-era codebase (commit 58bcf89).

## Affected products

- gkostka lwext4 1.0.0

## Timeline

- 2025-12-09: disclosed: Issue reported on GitHub repository
- 2026-06-01: advisory: CVE published to NVD

## References

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

## Related threats

- [gkostka lwext4 out-of-bounds read in ext4_ext_binsearch_idx](https://junglewise.ai/threats/cve-2025-70101-gkostka-lwext4-out-of-bounds-read-in-ext4-ext-binsearch-idx)
- [lwext4 divide-by-zero in ext4_block_set_lb_size](https://junglewise.ai/threats/cve-2025-70100-lwext4-divide-by-zero-in-ext4-block-set-lb-size)