Vulnerability in Gkostka Lwext4
CVE-2025-70100
A divide-by-zero vulnerability in the ext4_block_set_lb_size function in src/ext4_blockdev.c of the lwext4 1.0.0 library allows attackers to cause a denial of service by providing a malformed ext4 filesystem image that results in a zero logical block size. The vulnerability is triggered during mount or image processing and leads to a Floating-Point Exception (FPE) under sanitizers or a runtime crash in standard builds due to missing validation of lb_size.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.002 (4.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 5th percentile — 4.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- Gkostka Lwext4 — versions 1.0.0
Weakness classification (CWE)
References
- github.com/gkostka/lwext4/issues/90 (Exploit, Patch, Issue Tracking)
- github.com/sigdevel/pocs/blob/main/res/lwext4/2/sig8_2_lwext4_ext4_blockdev_c_1… (Exploit)
- infosec.exchange/@sigdevel/116668952003072580 (Exploit, Patch, Third Party Advisory)
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2025-70100?
- CVE-2025-70100 is a medium-severity vulnerability in Gkostka Lwext4, classified under Divide By Zero. CVSS score: 5.5/10. Published 2026-06-03.
- How severe is CVE-2025-70100?
- Medium severity. CVSS v3 base score is 5.5 out of 10.