# CVE-2026-109854: M17n-lib: uninitialized stack read in iso-2022 compound text utf-8 decoding

> Attackers can trigger uninitialized stack reads in M17n-lib during ISO-2022 decoding, potentially leaking sensitive memory contents to applications.

- **Severity:** Low 2.5 (`CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:N/A: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 Oct 2026
- **Updated:** 16 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-109854, GHSA-2f3f-m2rp-937p, UBUNTU-CVE-2026-109854

## What is CVE-2026-109854?

CVE-2026-109854 is a low-severity vulnerability in Red Hat Enterprise Linux 10, published on 13 Oct 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 m17n-lib. An attacker who supplies crafted input to an application processing ISO-2022 encoded text can cause the library to read uninitialized memory from the stack. If the application exposes or returns the decoded output, this flaw can result in unexpected behavior and limited information disclosure.

Weakness: CWE-457 (Use of Uninitialized Variable)

## Which versions are affected by CVE-2026-109854?


## How do I fix CVE-2026-109854?

Apply the vendor's patch.

## Is CVE-2026-109854 being exploited?

There is no known exploitation of CVE-2026-109854 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-109854 and fix it if it is affected.

What it is: CVE-2026-109854 is a low-severity vulnerability in Red Hat Enterprise Linux 10, published on 13 Oct 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-2026-109854 in the wild and no public exploit code.

Affected product: Red Hat Enterprise Linux 10. 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-2026-109854/ (Markdown: https://insights.sbomify.com/CVE-2026-109854/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-109854
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-109854
- OSV: https://osv.dev/vulnerability/CVE-2026-109854

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-109854/
Summaries are generated and may contain mistakes; the official description above is the record.