CVE-2018-6789
CRITICALCVSS 9.8/10Actively ExploitedEPSS 82.24%
Last modified
CVE-2018-6789 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. CISA has confirmed active exploitation in the wild. EPSS estimates a 82.24% chance of exploitation in the next 30 days.
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploitation Status
This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by .
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Exim | Exim | < 4.90.1 |
| Debian | Debian Linux | 7.0 |
| Debian | Debian Linux | 8.0 |
| Debian | Debian Linux | 9.0 |
| Canonical | Ubuntu Linux | 14.04 |
| Canonical | Ubuntu Linux | 16.04 |
| Canonical | Ubuntu Linux | 17.10 |
References
- http://openwall.com/lists/oss-security/2018/02/10/2Mailing List, Third Party Advisory
- http://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.htmlExploit, Third Party Advisory, VDB Entry
- http://www.openwall.com/lists/oss-security/2018/02/07/2Mailing List, Third Party Advisory
- http://www.securityfocus.com/bid/103049Broken Link, Third Party Advisory, VDB Entry
- http://www.securitytracker.com/id/1040461Broken Link, Third Party Advisory, VDB Entry
- https://devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2018-6789-en/Exploit, Third Party Advisory
- https://exim.org/static/doc/security/CVE-2018-6789.txtVendor Advisory
- https://lists.debian.org/debian-lts-announce/2018/02/msg00009.htmlMailing List, Third Party Advisory
- https://usn.ubuntu.com/3565-1/Third Party Advisory
- https://www.debian.org/security/2018/dsa-4110Mailing List, Third Party Advisory
- https://www.exploit-db.com/exploits/44571/Exploit, Third Party Advisory, VDB Entry
- https://www.exploit-db.com/exploits/45671/Exploit, Third Party Advisory, VDB Entry
- http://openwall.com/lists/oss-security/2018/02/10/2Mailing List, Third Party Advisory
- http://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.htmlExploit, Third Party Advisory, VDB Entry
- http://www.openwall.com/lists/oss-security/2018/02/07/2Mailing List, Third Party Advisory
- http://www.securityfocus.com/bid/103049Broken Link, Third Party Advisory, VDB Entry
- http://www.securitytracker.com/id/1040461Broken Link, Third Party Advisory, VDB Entry
- https://devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2018-6789-en/Exploit, Third Party Advisory
- https://exim.org/static/doc/security/CVE-2018-6789.txtVendor Advisory
- https://lists.debian.org/debian-lts-announce/2018/02/msg00009.htmlMailing List, Third Party Advisory
- https://usn.ubuntu.com/3565-1/Third Party Advisory
- https://www.debian.org/security/2018/dsa-4110Mailing List, Third Party Advisory
- https://www.exploit-db.com/exploits/44571/Exploit, Third Party Advisory, VDB Entry
- https://www.exploit-db.com/exploits/45671/Exploit, Third Party Advisory, VDB Entry
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-6789US Government Resource
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2018-6789?
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.
How severe is CVE-2018-6789?
CVE-2018-6789 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 82.24% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.
How do I fix CVE-2018-6789?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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