# CVE-2026-103679: tnef use-after-free and double-free in TNEF extraction

Source: https://junglewise.ai/threats/cve-2026-103679-a-flaw-was-found-in-tnef-a-remote-attacker-could-exploit-this  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-01. Updated: 2026-10-05  
License: CC BY 4.0 with a link back

CVE-2026-103679 · Severity: medium · CVSS 6.5 · Published 2026-10-01

tnef is a command-line utility for extracting attachments from Transport Neutral Encapsulation Format (TNEF) files, commonly used in email systems. A vulnerability in its memory handling allows an attacker to send a malicious TNEF file that causes the application to crash, resulting in a denial of service. This affects any system or user relying on tnef to automatically process email attachments.

Technologies: [Tnef Project Tnef](https://junglewise.ai/threats/technologies/tnef). Vendors: [Tnef Project](https://junglewise.ai/threats/vendors/tnef-project).

## Quick answers

**Is CVE-2026-103679 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-103679 being exploited in the wild.

**How severe is CVE-2026-103679?** Medium severity, with a CVSS score of 6.5, published 1 October 2026.

**Which products and versions are affected?** verdammelt tnef.

**Is there a fix for CVE-2026-103679?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-103679 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-103679?** Check whether you run Tnef Project Tnef or Verdammelt Tnef. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A use-after-free and double-free vulnerability exists in the get_body_files() function when processing TNEF files with multiple message bodies. The flaw is triggered during extraction of specially crafted TNEF files due to improper memory management. A remote attacker can send the malicious file to trigger a crash; no authentication or user interaction beyond receiving the file is required.

## Affected products

- verdammelt tnef

## Timeline

- 2026-10-01: disclosed

## References

- [https://github.com/verdammelt/tnef](https://github.com/verdammelt/tnef)
- [https://access.redhat.com/security/cve/CVE-2026-103679](https://access.redhat.com/security/cve/CVE-2026-103679)

## Related threats

- [A flaw was found in tnef. A heap-based buffer overflow can occur in the find_free_number() function when generating…](https://junglewise.ai/threats/cve-2026-103680-a-flaw-was-found-in-tnef-a-heap-based-buffer-overflow-can-occur)
- [tnef heap out-of-bounds read in RTF data parsing](https://junglewise.ai/threats/cve-2026-103678-a-flaw-was-found-in-tnef-an-attacker-can-exploit-this)