CVE-2018-6789
KEVRansomware UseExim Buffer Overflow Vulnerability
Description
Exim contains a buffer overflow vulnerability in the base64d function part of the SMTP listener that may allow for remote code execution.
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HPublishedFeb 8, 2018
Last modifiedJun 17, 2026
Added to KEVNov 3, 2021
Remediation dueMay 3, 2022
References
- openwall.com/lists/oss-security/2018/02/10/2Mailing ListThird Party Advisory
- packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.htmlExploitThird Party Advisory
- openwall.com/lists/oss-security/2018/02/07/2Mailing ListThird Party Advisory
- securityfocus.com/bid/103049Broken LinkThird Party Advisory
- securitytracker.com/id/1040461Broken LinkThird Party Advisory
- devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2018-6789-en/ExploitThird Party Advisory
- exim.org/static/doc/security/CVE-2018-6789.txtVendor Advisory
- git.exim.org/exim.git/commit/cf3cd306062a08969c41a1cdd32c6855f1abecf1Patch
- lists.debian.org/debian-lts-announce/2018/02/msg00009.htmlMailing ListThird Party Advisory
- usn.ubuntu.com/3565-1/Third Party Advisory
- debian.org/security/2018/dsa-4110Mailing ListThird Party Advisory
- exploit-db.com/exploits/44571/ExploitThird Party Advisory
0 recent articles mention this CVE
97
Risk assessment · Critical
Actively exploited and used by ransomware crews. Patch immediately.
- Exploitation
- Confirmed in the wild (CISA KEV)
- Federal remediation deadline
- Overdue by 1637 days
- Ransomware
- Used in known ransomware campaigns
- CVSS
- 9.8 CRITICAL
- EPSS (30-day exploit probability)
- 82.1% · top 1% of all CVEs
- Weakness
- CWE-120
- Attack vector
- Network, remotely reachable
- Preconditions
- No privileges and no user interaction
Recommended actions
- 1.Apply updates per vendor instructions.
- 2.Treat as emergency change: patch or isolate internet-facing instances first.
- 3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
- 4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.
- 5.Verify offline/immutable backups and segment the affected systems. This flaw is used for ransomware initial access.
Assessment is derived automatically from the live signals above; verify against your own asset inventory.