CVE-2018-6789
CriticalExploitedPublic exploitBy sending a handcrafted message, a buffer overflow may happen.
Published Feb 8, 2018 · Updated Aug 4, 2026 · Also known as DEBIAN-CVE-2018-6789, DLA-1274-1, DSA-4110-1, UBUNTU-CVE-2018-6789, USN-3565-1
Key Facts
Patch immediately- CVE-2018-6789 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting Exim, Ubuntu Linux (Canonical), Debian Linux and 10 more products.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Feb 25, 2020 and is known to be used in ransomware campaigns. Public exploit code is available.
- EPSS estimates a 82% probability of exploitation in the next 30 days.
- Fixed versions are available, including Exim 4.86.2-20.1, Exim 4.90.1-1, Exim 4.90.1-2.14.amzn1.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
82%
Higher than 99.6% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings, used by ransomware
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2018-6789 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Nov 3, 2021 | May 3, 2022 | Known |
| Industry KEV feed | Feb 25, 2020 | May 3, 2022 | Known |
| CIRCL KEV | Nov 3, 2021 | May 3, 2022 | Known |
| ENISA EUVD | Nov 3, 2021 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
66 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| EximExim | See advisory | 4.90.1 |
| Ubuntu LinuxCanonical | 14.04, 16.04, 17.10 | n/a |
| Debian LinuxDebian | 7.0, 8.0, 9.0 | n/a |
| exim4debian | See advisory | 4.90.1-1 |
| exim-greylistamazon | See advisory | 4.90.1-2.14.amzn1 |
Patched Releases
Exim
4.86.2-20.1, 4.90.1-1, 4.90.1-2.14.amzn1, 4.90.1-r0, 4.94.2-4.2, 4.94.2-bp151.2.4.1, 4.94.2-bp152.6.4.1, 4.94.2-lp152.8.3.1, 4.90.1
exim-greylist
4.90.1-2.14.amzn1
exim-mon
4.90.1-2.14.amzn1
exim-mysql
4.90.1-2.14.amzn1
exim-pgsql
4.90.1-2.14.amzn1
exim4
4.80-7+deb7u6, 4.82-3ubuntu2.4, 4.84.2-2+deb8u5, 4.86.2-2ubuntu2.3, 4.89-2+deb9u3, 4.90.1-1
eximon
4.86.2-20.1, 4.94.2-4.2, 4.94.2-bp151.2.4.1, 4.94.2-bp152.6.4.1, 4.94.2-lp152.8.3.1
eximstats-html
4.86.2-20.1, 4.94.2-4.2, 4.94.2-bp151.2.4.1, 4.94.2-bp152.6.4.1, 4.94.2-lp152.8.3.1
libspf2-2
1.2.10-bp151.4.1, 1.2.10-bp152.5.1
libspf2-devel
1.2.10-bp151.4.1, 1.2.10-bp152.5.1
libspf2-tools
1.2.10-bp151.4.1, 1.2.10-bp152.5.1
Timeline
Publicly disclosed
Feb 8, 2018
Added to Industry KEV feed
Feb 25, 2020
Added to CISA KEV
Nov 3, 2021
Added to CIRCL KEV
Nov 3, 2021
Added to ENISA EUVD
Nov 3, 2021
Last updated
Aug 4, 2026
Weakness Type
- CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
References
- advisoryhttp://openwall.com/lists/oss-security/2018/02/10/2
- advisoryhttps://exim.org/static/doc/security/CVE-2018-6789.txt
- advisory[debian-lts-announce] 20180210 [SECURITY] [DLA 1274-1] exim4 security update
- advisoryhttps://security-tracker.debian.org/tracker/CVE-2018-6789
- advisoryhttps://ubuntu.com/security/CVE-2018-6789
FAQ
Common Questions.
An issue was discovered in the base64d function in the SMTP listener in Exim before 4.90.1.
Affected: Exim; Ubuntu Linux (Canonical) versions 14.04, 16.04, 17.10; Debian Linux versions 7.0, 8.0, 9.0, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Feb 25, 2020 and is known to be used in ransomware campaigns.
Yes. It was added on Nov 3, 2021 with a federal remediation due date of May 3, 2022.
Public exploit code is available.
Fixed versions are available, including Exim 4.86.2-20.1, Exim 4.90.1-1, Exim 4.90.1-2.14.amzn1.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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