# CVE-2026-31449: ext4: validate p_idx bounds in ext4_ext_correct_indexes

> A local attacker can trigger a slab-out-of-bounds read in the ext4 filesystem by crafting a corrupted extent header, potentially causing a system crash or information disclosure.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 22 Apr 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-83273, BELL-CVE-2026-31449, DEBIAN-CVE-2026-31449, GHSA-rq43-8p3g-5cc4, ROOT-OS-DEBIAN-11-CVE-2026-31449, ROOT-OS-DEBIAN-12-CVE-2026-31449, ROOT-OS-DEBIAN-13-CVE-2026-31449, ROOT-OS-UBUNTU-2204-CVE-2026-31449, ROOT-OS-UBUNTU-2404-CVE-2026-31449, UBUNTU-CVE-2026-31449

## What is CVE-2026-31449?

CVE-2026-31449 is a high-severity memory corruption vulnerability in Linux kernel, published on 22 Apr 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-31449?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31449?

Apply the vendor's patch.

## Is CVE-2026-31449 being exploited?

There is no known exploitation of CVE-2026-31449 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31449 and fix it if it is affected.

What it is: CVE-2026-31449 is a high-severity memory corruption vulnerability in Linux kernel, published on 22 Apr 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-31449 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-31449/ (Markdown: https://insights.sbomify.com/CVE-2026-31449/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31449
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31449
- OSV: https://osv.dev/vulnerability/CVE-2026-31449

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31449/
Summaries are generated and may contain mistakes; the official description above is the record.