Exim up to 4.99.0 heap-based overflow

Summaryinfo

A vulnerability, which was classified as critical, has been found in Exim up to 4.99.0. Impacted is an unknown function. The manipulation leads to heap-based overflow. This vulnerability is uniquely identified as CVE-2025-67896. The attack is possible to be carried out remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Exim up to 4.99.0 and classified as critical. This issue affects an unknown functionality. The manipulation with an unknown input leads to a heap-based overflow vulnerability. Using CWE to declare the problem leads to CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Exim before 4.99.1, with certain non-default rate-limit configurations, allows a remote heap-based buffer overflow because database records are cast directly to internal structures without validation.

It is possible to read the advisory at openwall.com. The identification of this vulnerability is CVE-2025-67896 since 12/14/2025. The exploitation is known to be difficult. The attack may be initiated remotely. The technical details are unknown and an exploit is not publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 278629 (Linux Distros Unpatched Vulnerability : CVE-2025-67896), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 4.99.1 eliminates this vulnerability.

The vulnerability is also documented in the databases at CNNVD (CNNVD-202512-2604), Tenable (278629), EUVD (EUVD-2025-203281) and CERT Bund (WID-SEC-2025-2840). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Fedora Linux
• Open Source Exim

Productinfo

Type

• Mail Server Software

Name

• Exim

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13
• 4.14
• 4.15
• 4.16
• 4.17
• 4.18
• 4.19
• 4.20
• 4.21
• 4.22
• 4.23
• 4.24
• 4.25
• 4.26
• 4.27
• 4.28
• 4.29
• 4.30
• 4.31
• 4.32
• 4.33
• 4.34
• 4.35
• 4.36
• 4.37
• 4.38
• 4.39
• 4.40
• 4.41
• 4.42
• 4.43
• 4.44
• 4.45
• 4.46
• 4.47
• 4.48
• 4.49
• 4.50
• 4.51
• 4.52
• 4.53
• 4.54
• 4.55
• 4.56
• 4.57
• 4.58
• 4.59
• 4.60
• 4.61
• 4.62
• 4.63
• 4.64
• 4.65
• 4.66
• 4.67
• 4.68
• 4.69
• 4.70
• 4.71
• 4.72
• 4.73
• 4.74
• 4.75
• 4.76
• 4.77
• 4.78
• 4.79
• 4.80
• 4.81
• 4.82
• 4.83
• 4.84
• 4.85
• 4.86
• 4.87
• 4.88
• 4.89
• 4.90
• 4.91
• 4.92
• 4.93
• 4.94
• 4.95
• 4.96
• 4.97
• 4.98
• 4.99.0

License

• open-source

CPE 2.3info

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CPE 2.2info

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Entryinfo

Be aware that VulDB is the high quality source for vulnerability data.

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