CVE DATABASE / CVE-2018-6789
CVE-2018-6789
Exim Buffer Overflow Vulnerability
CVSS 9.8 · CRITICAL
⚠ CISA KEV — ACTIVELY EXPLOITED
RANSOMWARE
On the CISA KEV catalog
Confirmed exploited in the wild. Added 2021-11-03.
Federal remediation due 2022-05-03.
Required action: Apply updates per vendor instructions.
Summary
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 3.1 breakdown
| Base score | 9.8 (CRITICAL) |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| Attack vector | NETWORK |
| Attack complexity | LOW |
| Privileges required | NONE |
| User interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality | HIGH |
| Integrity | HIGH |
| Availability | HIGH |
Weakness type (CWE)
Affected products
Exim eximDebian debian linuxCanonical ubuntu linux
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References
- http://openwall.com/lists/oss-security/2018/02/10/2
- http://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.html
- http://www.openwall.com/lists/oss-security/2018/02/07/2
- http://www.securityfocus.com/bid/103049
- http://www.securitytracker.com/id/1040461
- https://devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2018-6789-en/
- https://exim.org/static/doc/security/CVE-2018-6789.txt
- https://git.exim.org/exim.git/commit/cf3cd306062a08969c41a1cdd32c6855f1abecf1
- https://lists.debian.org/debian-lts-announce/2018/02/msg00009.html
- https://usn.ubuntu.com/3565-1/
- https://www.debian.org/security/2018/dsa-4110
- https://www.exploit-db.com/exploits/44571/
- https://www.exploit-db.com/exploits/45671/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-6789
Data: NIST NVD + CISA KEV. NVD last modified 2025-11-07. Always verify against the vendor advisory before acting.