CVE-2026-43067: Linux Kernel

Critical severity, CVSS 9.8. EPSS: 0.7% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: ext4: handle wraparound when searching for blocks for indirect mapped blocks Commit 4865c768b563 ("ext4: always allocate blocks only from groups inode can use") restricts what blocks will be allocated for indirect block based files to block numbers that fit within 32-bit block numbers. However, when using a review bot running on the latest Gemini LLM to check this commit when backporting into an LTS based kernel, it raised this concern: If ac->ac_g_ex.fe_group is >= ngroups (for instance, if the goal group was populated via stream allocation from s_mb_last_groups), then start will be >= ngroups. Does this allow allocating blocks beyond the 32-bit limit for indirect block mapped files? The commit message mentions that ext4_mb_scan_groups_linear() takes care to not select unsupported groups. However, its loop uses group = *start, and the very first iteration will call ext4_mb_scan_group() with this unsupported group because next_linear_group() is only called at the end of the iteration. After reviewing the code paths involved and considering the LLM review, I determined that this can happen when there is a file system where some files/directories are extent-mapped and others are indirect-block mapped. To address this, add a safety clamp in ext4_mb_scan_groups().

Affected products

• Linux Linux Kernel: from 5.15.203, before 5.16 (fixed in 5.16); from 6.6.130, before 6.6.134 (fixed in 6.6.134); from 6.12.77, before 6.12.80 (fixed in 6.12.80); from 6.18.14, before 6.18.21 (fixed in 6.18.21); from 6.19.4, before 6.19.11 (fixed in 6.19.11); version 6.1.167 only

Published 2026-05-05. Last modified 2026-06-17.