# CVE-2026-5673: Libtheora: libtheora: denial of service or information disclosure via malformed avi file processing

> A local attacker can cause a crash or leak heap memory by tricking a user into opening a malformed AVI file processed by libtheora.

- **Severity:** Medium 5.6 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 6 Apr 2026
- **Updated:** 1 May 2026
- **Also known as:** DEBIAN-CVE-2026-5673, ECHO-5fc2-c517-ff68, GHSA-cjcp-vc46-rm2h, OESA-2026-2210, ROOT-OS-DEBIAN-13-CVE-2026-5673, UBUNTU-CVE-2026-5673

## What is CVE-2026-5673?

CVE-2026-5673 is a medium-severity vulnerability in Redhat Enterprise Linux, published on 6 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

A flaw was found in libtheora. This heap-based out-of-bounds read vulnerability exists within the AVI (Audio Video Interleave) parser, specifically in the avi_parse_input_file() function. A local attacker could exploit this by tricking a user into opening a specially crafted AVI file containing a truncated header sub-chunk. This could lead to a denial-of-service (application crash) or potentially leak sensitive information from the heap.

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

## Which versions are affected by CVE-2026-5673?

It affects 2 products.


Products: Redhat Enterprise Linux, Xiph Theora.

## How do I fix CVE-2026-5673?

Apply the vendor's patch.

## Is CVE-2026-5673 being exploited?

There is no known exploitation of CVE-2026-5673 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2018-14667](https://insights.sbomify.com/CVE-2018-14667/): Red Hat JBoss RichFaces Framework Expression Language Injection (critical 9.8, exploited in the wild)
- [CVE-2021-20325](https://insights.sbomify.com/CVE-2021-20325/): Missing fixes for CVE-2021-40438 and CVE-2021-26691 in the versions of httpd, as shipped in Red Hat Enterprise Linux 8.5.0, causes a securit (critical 9.8)
- [CVE-2018-25011](https://insights.sbomify.com/CVE-2018-25011/): Memory corruption in libwebp (critical 9.8)
- [CVE-2018-25014](https://insights.sbomify.com/CVE-2018-25014/): Other in libwebp (critical 9.8)
- [CVE-2014-3585](https://insights.sbomify.com/CVE-2014-3585/): Supply chain in redhat-upgrade-tool (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-5673 and fix it if it is affected.

What it is: CVE-2026-5673 is a medium-severity vulnerability in Redhat Enterprise Linux, published on 6 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-2026-5673 in the wild and no public exploit code.

Affected product: Redhat Enterprise Linux. 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-2026-5673/ (Markdown: https://insights.sbomify.com/CVE-2026-5673/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-5673
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-5673
- OSV: https://osv.dev/vulnerability/CVE-2026-5673

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-5673/
Summaries are generated and may contain mistakes; the official description above is the record.