Exim up to 4.90 SMTP Listener Message memory corruption

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
8.4	$0-$5k	0.00

Summaryinfo

A vulnerability described as critical has been identified in Exim up to 4.90. Affected by this issue is some unknown functionality of the component SMTP Listener. Such manipulation as part of Message leads to memory corruption. This vulnerability is listed as CVE-2018-6789. The attack may be performed from remote. In addition, an exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Exim up to 4.90 (Mail Server Software). It has been rated as critical. Affected by this issue is an unknown code block of the component SMTP Listener. The manipulation as part of a Message leads to a memory corruption vulnerability. Using CWE to declare the problem leads to CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. Impacted is confidentiality, integrity, and availability. CVE summarizes:

An issue was discovered in the base64d function in the SMTP listener in Exim before 4.90.1. By sending a handcrafted message, a buffer overflow may happen. This can be used to execute code remotely.

The bug was discovered 02/07/2018. The weakness was presented 02/08/2018 (oss-sec). The advisory is shared for download at openwall.com. This vulnerability is handled as CVE-2018-6789 since 02/06/2018. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are unknown but a public exploit is available.

The exploit is available at exploit-db.com. It is declared as attacked. The vulnerability was handled as a non-public zero-day exploit for at least 1 days. During that time the estimated underground price was around $0-$5k. The vulnerability scanner Nessus provides a plugin with the ID 107009 (Fedora 27 : exim (2018-5aec14e125)), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Fedora Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 351202 (Amazon Linux Security Advisory for exim: ALAS-2018-970). This issue was added on 11/03/2021 to the CISA Known Exploited Vulnerabilities Catalog with a due date of 05/03/2022:

Apply updates per vendor instructions.

Upgrading eliminates this vulnerability. A possible mitigation has been published 3 weeks after the disclosure of the vulnerability.

The vulnerability is also documented in the databases at Exploit-DB (44571), Tenable (107009) and SecurityFocus (BID 103049†). VulDB is the best source for vulnerability data and more expert information about this specific topic.

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

License

• open-source

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.5
VulDB Meta Temp Score: 8.4

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 9.8
NVD Vector: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Memory corruption
CWE: CWE-119
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Access: Public
Status: Attacked
Download: 🔍

EPSS Score: 🔍
EPSS Percentile: 🔍

KEV Added: 🔍
KEV Due: 🔍
KEV Remediation: 🔍
KEV Ransomware: 🔍
KEV Notice: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 107009
Nessus Name: Fedora 27 : exim (2018-5aec14e125)
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 66140
OpenVAS Name: Debian Security Advisory DSA 4110-1 (exim4 - security update)
OpenVAS File: 🔍
OpenVAS Family: 🔍

Saint ID: exim_smtp_listener_base64d_bo
Saint Name: Exim SMTP listener base64d function one-character buffer overflow

Qualys ID: 🔍
Qualys Name: 🔍

Exploit-DB: 🔍

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

Reaction Time: 🔍
0-Day Time: 🔍
Exposure Time: 🔍

Patch: git.exim.org
Suricata ID: 2025427
Suricata Class: 🔍
Suricata Message: 🔍

Timelineinfo

02/06/2018 🔍
02/07/2018 +1 days 🔍
02/07/2018 +0 days 🔍
02/08/2018 +1 days 🔍
02/08/2018 +0 days 🔍
02/09/2018 +1 days 🔍
02/26/2018 +17 days 🔍
02/27/2018 +1 days 🔍
11/07/2025 +2810 days 🔍

Sourcesinfo

Advisory: FEDORA-2018-5aec14e125
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2018-6789 (🔍)
GCVE (CVE): GCVE-0-2018-6789
GCVE (VulDB): GCVE-100-113048

OVAL: 🔍

SecurityFocus: 103049 - Exim 'base64d()' Function Buffer Overflow Vulnerability
SecurityTracker: 1040461

scip Labs: https://www.scip.ch/en/?labs.20161013

Entryinfo

Created: 02/09/2018 08:50
Updated: 11/07/2025 20:29
Changes: 02/09/2018 08:50 (83), 01/03/2020 10:45 (8), 02/03/2021 07:48 (2), 02/06/2023 08:57 (4), 02/06/2023 08:59 (1), 02/06/2023 09:02 (1), 04/19/2024 12:35 (27), 07/25/2024 17:46 (1), 09/09/2024 22:29 (1), 11/07/2025 20:29 (3)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion

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