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CVE-2018-6789

CRITICAL
9.8
CVSS Score
Published: February 8, 2018 at 11:00 PM UTC
Updated: June 17, 2026 at 02:02 AM UTC
3 products affected across 3 vendorsDebian LinuxUbuntu LinuxExim

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Severity
CRITICAL9.8
Exploitation
CISA KEV
Exploit prediction
EPSS 82%
SSVC
Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score82.1%

EPSS (Exploit Prediction Scoring System) estimates a 82.1% chance this CVE is exploited in the wild within the next 30 days — higher than 100% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

Exim contains a buffer overflow vulnerability in the base64d function part of the SMTP listener that may allow for remote code execution.

Required Action
Apply updates per vendor instructions.
Ransomware Use
Known
Added to KEV
Nov 3, 2021
Remediation Due
May 3, 2022
1638 days overdue
Notes
https://nvd.nist.gov/vuln/detail/CVE-2018-6789

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Ubuntu Linux· Canonicalrubygems
95%
14.0416.0417.10
Debian Linux· Debiandrupal
95%
7.08.09.0
Exim· Exim
95%
v < 4.90.1
Affected range stops below 4.90.1, so it looks safe — our inference, not a vendor statement

References (14)

x_refsource_CONFIRMMailing ListThird Party Advisory
Source: [email protected]
http://openwall.com/lists/oss-security/2018/02/10/2
x_refsource_MISCExploitThird Party AdvisoryVDB Entry
Source: [email protected]
http://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.html
Mailing Listx_refsource_MLISTThird Party Advisory
Source: [email protected]
http://www.openwall.com/lists/oss-security/2018/02/07/2
VDB Entryx_refsource_BIDBroken LinkThird Party Advisory
Source: [email protected]
http://www.securityfocus.com/bid/103049
VDB Entryx_refsource_SECTRACKBroken LinkThird Party Advisory
Source: [email protected]
http://www.securitytracker.com/id/1040461
x_refsource_MISCExploitThird Party Advisory
Source: [email protected]
https://devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2018-6789-en/
x_refsource_CONFIRMVendor Advisory
Source: [email protected]
https://exim.org/static/doc/security/CVE-2018-6789.txt
x_refsource_CONFIRMPatch
Source: [email protected]
https://git.exim.org/exim.git/commit/cf3cd306062a08969c41a1cdd32c6855f1abecf1

SSVC — Action Prioritization

SSVCActiveAutomatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

9.8CRITICALCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-120

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