---
id: CVE-2026-103680
title: A flaw was found in tnef
summary: >-
  A flaw was found in tnef. A heap-based buffer overflow can occur in the
  find_free_number() function when generating numbered backup suffixes for
  duplicate filenames. When numbered backups are enabled and file overwriting is
  disabled, an …
severity: low
cvss: 3.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L'
cwe:
  - CWE-787
product: tnef
affected:
  - tnef <= 1.4.18
published: '2026-10-01'
updated: '2026-10-01'
sourceUpdated: '2026-10-01T13:02:09.610'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-103680'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-103680'
    label: patrick@puiterwijk.org
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2544478'
    label: patrick@puiterwijk.org
  - url: 'https://github.com/verdammelt/tnef'
    label: patrick@puiterwijk.org
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-01T12:43:54.811Z'
---

## Overview

A flaw was found in tnef. A heap-based buffer overflow can occur in the find_free_number() function when generating numbered backup suffixes for duplicate filenames. When numbered backups are enabled and file overwriting is disabled, an attacker can supply a specially crafted Transport Neutral Encapsulation Format (TNEF) file with an excessive number of colliding attachment filenames, causing the numeric counter to write past the allocated memory buffer. This issue may result in an application crash, leading to a Denial of Service (DoS), or potentially arbitrary code execution.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.