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CVE-2026-103680

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

3.1 Low

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
Low

Exploit likelihood

0.32%Unchanged since Oct 2, 2026
90%50%10%1%

What each source reports

CVE List Score used 3.1

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

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.

Record
CVE-2026-103680
CVSS 3.1
3.1 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
Weakness
CWE-787
Updated
2026-11-02
EUVDEUVD-2026-90773 3.1

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.

Record
EUVD-2026-90773
CVSS 3.1
3.1 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
Updated
2026-11-02
GitHub AdvisoriesGHSA-qr96-v34j-wcrq 3.1

A flaw was found in tnef. A heap-based buffer overflow can occur in the find_free_number()...

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.

Record
GHSA-qr96-v34j-wcrq
CVSS 3.1
3.1 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
Weakness
CWE-787
Updated
2026-11-02
NVD 3.1

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.

Record
CVE-2026-103680
CVSS 3.1
3.1 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Weakness
CWE-787
Updated
2026-11-02
OSV 3.1

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

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.

Record
CVE-2026-103680
CVSS 3.1
3.1 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
Weakness
CWE-787
Updated
2026-11-02
OSVDEBIAN-CVE-2026-103680 6.5

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.

Record
DEBIAN-CVE-2026-103680
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-103680 3.1

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.

Record
UBUNTU-CVE-2026-103680
CVSS 3.1
3.1 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
tnef
Debian:12
All versions, plus listed versions
1.4.18-31.4.18-41.4.18-51.4.18-6
None known
tnef
Debian:13
All versions, plus listed versions
1.4.18-41.4.18-51.4.18-6
None known
tnef
Debian:14
All versions, plus listed versions
1.4.18-41.4.18-51.4.18-6
None known
tnef
Ubuntu:16.04:LTS
All versions, plus listed versions
1.4.9-11.4.9-1+deb8u2build0.16.04.11.4.9-1+deb8u3build0.16.04.11.4.9-1+deb8u4build0.16.04.1
None known
tnef
Ubuntu:18.04:LTS
All versions, plus listed versions
1.4.12-1.2
None known
tnef
Ubuntu:20.04:LTS
All versions, plus listed versions
1.4.12-1.21.4.18-1
None known
tnef
Ubuntu:22.04:LTS
All versions, plus listed versions
1.4.18-3
None known
tnef
Ubuntu:24.04:LTS
All versions, plus listed versions
1.4.18-3
None known
tnef
Ubuntu:26.10
All versions, plus listed versions
1.4.18-5build11.4.18-6
None known
tnef
Ubuntu:26.04:LTS
All versions, plus listed versions
1.4.18-51.4.18-5build1
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-103680 is a low vulnerability (CVSS 3.1) in Tnef Project Tnef, published October 1, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.32%, the 25th percentile. No source names a fixed version.

References

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