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Vulnerability · Published Oct 1, 2026 · Assigned by fedora

CVE-2026-103680Tnef: heap buffer overflow in find_free_number() via numbered-backup suffix generation

Low 3.1

In plain English

A low-severity out-of-bounds write in tnef. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 25% of all known vulnerabilities).

Severity (CVSS 3.1)3.1Low
Exploit odds (30 days)0.3%top 74.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12tnefno fix listedDEBIAN-CVE-2026-103680
Debian:13tnefno fix listedDEBIAN-CVE-2026-103680
Debian:14tnefno fix listedDEBIAN-CVE-2026-103680
Ubuntu:22.04:LTStnefno fix listedUBUNTU-CVE-2026-103680
Ubuntu:24.04:LTStnefno fix listedUBUNTU-CVE-2026-103680
Ubuntu:26.04:LTStnefno fix listedUBUNTU-CVE-2026-103680
Ubuntu:26.10tnefno fix listedUBUNTU-CVE-2026-103680

Affected products (as reported)

VendorProductVersions
tnef 0 – through 1.4.18

Weakness: CWE-787 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L

References