CVE-2018-6789: Exim Buffer Overflow Vulnerability
Vulnerability summary
CVE-2018-6789 is a critical (CVSS 9.8) Classic Buffer Overflow vulnerability in Exim. It is known to be exploited: CISA lists it, first on 03-11-2021. It has been used in ransomware campaigns. EPSS estimates a 82.14% chance of exploitation in the next 30 days, higher than 99.6% of scored vulnerabilities. 4 public exploits are recorded.
Advisory lineage
Upstream 0 · Downstream 4 · Related 4Timeline
- 08-02-2018PublishedVulnerability first disclosed.
- 03-11-2021Added to CISA KEVExim Buffer Overflow Vulnerability
- 03-05-2022CISA remediation dueApply updates per vendor instructions.
- 21-10-2025Last modifiedVulnerability information updated.
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.
CVSS metrics
6 scores · 4 sources · 3 versions- NVDNIST9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
82.14%
Chance of exploitation in the next 30 days
Percentile
100%
Versus all other CVEs
30-day change
0.00 pp
From 82.14% on 18-09-2026
Known exploited
Compare KEV catalogs
CISA KEVListed- Added
- 03-11-2021
- Federal due date
- 03-05-2022
CISA required action
Apply updates per vendor instructions. nvd.nist.gov/vuln/detail/CVE-2018-6789
Public exploits
4 foundExploit Reference (devco.re)
Maturity: unknown
Exploit Reference (packetstormsecurity.com)
Maturity: unknown
exim 4.90 - Remote Code Execution
Maturity: poc
Weaknesses
CWE · root causeAffected systems
Debian2 products
- exim4< 4.90.1-1 | < 4.84.2-2+deb8u5 | < 4.89-2+deb9u3 | < 4.80-7+deb7u6
- debian_linuxEOL7.0 | 8.0 | 9.0
Canonical1 product
- ubuntu_linuxEOL14.04 | 16.04 | 17.10
Exim1 product
- exim< 4.90.1
Ubuntu1 product
- exim4< 4.82-3ubuntu2.4 | < 4.86.2-2ubuntu2.3
4 vendors · 5 products
References
19 links- www.openwall.com/lists/oss-security/2018/02/07/2Mailing ListX Refsource MLISTThird Party AdvisoryREPORT
www.debian.org/security/2018/dsa-4110Vendor AdvisoryX Refsource DEBIANMailing ListThird Party Advisory- lists.debian.org/debian-lts-announce/2018/02/msg00009.htmlMailing ListX Refsource MLISTThird Party Advisory
- devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2018-6789-en/X Refsource MISCExploitThird Party Advisory
Show all 19 references
- packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.htmlX Refsource MISCExploitThird Party AdvisoryVDB Entry
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-6789Government ResourceUS Government Resource