# CVE-2026-90783: MKVToolNix through 101.0 Heap Buffer Overflow via avilib ODML Superindex Integer Wraparound

> Attackers can trigger a heap buffer overflow in MKVToolNix by crafting a malicious AVI file, potentially leading to code execution or denial of service.

- **Severity:** High 8.5 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **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:** 13 Sep 2026
- **Updated:** 30 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-90783, GHSA-x9xf-h66v-mjmc, UBUNTU-CVE-2026-90783, openSUSE-SU-2026:11779-1, openSUSE-SU-2026:21867-1

## What is CVE-2026-90783?

CVE-2026-90783 is a high-severity vulnerability in Moritz Bunkus MKVToolNix, published on 13 Sep 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

MKVToolNix through 101.0 contains a heap buffer overflow in the bundled avilib library's ODML superindex parser due to integer wraparound in 32-bit arithmetic. Attackers can craft a malicious AVI file with oversized entry counts that cause an undersized heap allocation, allowing a heap buffer overflow when the file is parsed with mkvmerge.

Weakness: CWE-680 (Integer Overflow to Buffer Overflow)

## Which versions are affected by CVE-2026-90783?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mkvtoolnix` | openSUSE:Leap 16.0 | All versions | 95.0-bp160.2.1 |
| `mkvtoolnix` | openSUSE:Tumbleweed | All versions | 101.0-2.1 |

## How do I fix CVE-2026-90783?

Apply the vendor's patch.

## Is CVE-2026-90783 being exploited?

There is no known exploitation of CVE-2026-90783 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90783 and fix it if it is affected.

What it is: CVE-2026-90783 is a high-severity vulnerability in Moritz Bunkus MKVToolNix, published on 13 Sep 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-2026-90783 in the wild and no public exploit code.

Affected product: Moritz Bunkus MKVToolNix. 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-2026-90783/ (Markdown: https://insights.sbomify.com/CVE-2026-90783/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90783
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90783
- OSV: https://osv.dev/vulnerability/CVE-2026-90783

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90783/
Summaries are generated and may contain mistakes; the official description above is the record.