CVE-2026-103680 Tnef: heap buffer overflow in find_free_number() via numbered-backup suffix generation
Heap buffer overflow in tnef library allows DoS or code execution via crafted TNEF files when numbered backups are enabled.
- 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
- None listed
What is CVE-2026-103680?
CVE-2026-103680 is a low-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. 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.
Weakness: CWE-787
Which versions are affected by CVE-2026-103680?
It affects 1 product.
Products include Tnef Project Tnef.
How do I fix CVE-2026-103680?
No fix has been published for CVE-2026-103680 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-103680 being exploited?
There is no known exploitation of CVE-2026-103680 in the wild and no public exploit code.
Other vulnerabilities in tnef_project:tnef
Sources
Also known as DEBIAN-CVE-2026-103680, GHSA-qr96-v34j-wcrq, UBUNTU-CVE-2026-103680.