# CVE-2026-104266: tinytag: Infinite loop when parsing certain M4A files containing invalid atoms

> Attackers can cause a denial of service in applications using tinytag by providing crafted M4A files that trigger an infinite loop during metadata parsing.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 15 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-104266, GHSA-24cc-9352-h2pg, UBUNTU-CVE-2026-104266

## What is CVE-2026-104266?

CVE-2026-104266 is a medium-severity denial of service vulnerability in tinytag, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

tinytag is a Python library for reading audio file metadata. From 2.0.0 until 2.3.0, an M4A file containing a sub-atom with a size of zero inside a ---- atom can cause the metadata parser to stop advancing through the input. The custom-field atom traversal repeatedly processes the malformed location, causing an infinite loop and denying service to a program that reads the crafted file. This issue is fixed in version 2.3.0.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2026-104266?

2 open source packages ship an affected version, including tinytag.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `tinytag` | PyPI | From 2.0.0 | 2.3.0 |
| `tinytag` | PyPI | From 2.0.0 | 2.3.0 |

## How do I fix CVE-2026-104266?

Upgrade tinytag to 2.3.0 or later.

## Is CVE-2026-104266 being exploited?

There is no known exploitation of CVE-2026-104266 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-104266 and fix it if it is affected.

What it is: CVE-2026-104266 is a medium-severity denial of service vulnerability in tinytag, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-104266 in the wild and no public exploit code.

Affected packages and fixed versions:
- tinytag (PyPI): affected from 2.0.0; fixed in 2.3.0
- tinytag (PyPI): affected from 2.0.0; fixed in 2.3.0

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-2026-104266/ (Markdown: https://insights.sbomify.com/CVE-2026-104266/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-104266
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104266
- OSV: https://osv.dev/vulnerability/CVE-2026-104266

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-104266/
Summaries are generated and may contain mistakes; the official description above is the record.