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
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
- https://openwall.com/lists/oss-security/2018/02/10/2Mailing List, Third Party Advisory
- https://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.htmlExploit, Third Party Advisory, VDB Entry
- https://www.openwall.com/lists/oss-security/2018/02/07/2Mailing List, Third Party Advisory
- https://www.securityfocus.com/bid/103049Broken Link, Third Party Advisory, VDB Entry
- https://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://openwall.com/lists/oss-security/2018/02/10/2Mailing List, Third Party Advisory
- https://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.htmlExploit, Third Party Advisory, VDB Entry
- https://www.openwall.com/lists/oss-security/2018/02/07/2Mailing List, Third Party Advisory
- https://www.securityfocus.com/bid/103049Broken Link, Third Party Advisory, VDB Entry
- https://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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