# CVE-2026-103678: Tnef: heap out-of-bounds read in get_rtf_data_from_buf() via uncompressed rtf mapi value

> An attacker can cause a crash or leak memory by providing a crafted file with uncompressed RTF data to the TNEF library.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L`)
- **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:** No
- **Published:** 1 Oct 2026
- **Updated:** 1 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-103678, GHSA-8r4j-263j-fh85, UBUNTU-CVE-2026-103678

## What is CVE-2026-103678?

CVE-2026-103678 is a medium-severity memory corruption vulnerability in tnef_project:tnef, published on 1 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

A flaw was found in tnef. An attacker can exploit this vulnerability by providing a specially crafted file containing uncompressed Rich Text Format (RTF) data. Because the application fails to properly validate input buffer boundaries before copying data in get_rtf_data_from_buf(), reading beyond the allocated memory occurs. This flaw can cause the application to crash, leading to a Denial of Service (DoS), or leak sensitive memory contents into extracted output files.

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

## Which versions are affected by CVE-2026-103678?

It affects 1 product.


Products: Tnef Project Tnef.

## How do I fix CVE-2026-103678?

No fix has been published for CVE-2026-103678 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-103678 being exploited?

There is no known exploitation of CVE-2026-103678 in the wild and no public exploit code.

## Other vulnerabilities in tnef_project:tnef

- [CVE-2017-8911](https://insights.sbomify.com/CVE-2017-8911/): Integer overflow in n/a (critical 9.8)
- [CVE-2026-103679](https://insights.sbomify.com/CVE-2026-103679/): Tnef: use-after-free and double-free in get_body_files() via multi-value body extraction (medium 6.5)
- [CVE-2026-103680](https://insights.sbomify.com/CVE-2026-103680/): Tnef: heap buffer overflow in find_free_number() via numbered-backup suffix generation (low 3.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-103678 and fix it if it is affected.

What it is: CVE-2026-103678 is a medium-severity memory corruption vulnerability in tnef_project:tnef, published on 1 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-2026-103678 in the wild and no public exploit code.

Affected product: tnef_project:tnef. 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-2026-103678/ (Markdown: https://insights.sbomify.com/CVE-2026-103678/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-103678
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-103678
- OSV: https://osv.dev/vulnerability/CVE-2026-103678

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-103678/
Summaries are generated and may contain mistakes; the official description above is the record.