What it is
CVE-2018-6789 is an unauthenticated vulnerability affecting Exim. 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...
Vulnerability report
Exploited in the wild
Confirmed confidence
In CISA KEV
CVE-2018-6789
Exim
- Severity
- CVSS 9.8 · Critical
- Confidence
- Confirmed
- Exploit status
- Exploited in the wild
- EPSS
- 82.1%
- First observed
- —
- Last observed
- —
Decision summary
What security teams need to know first
Direct answers before the deeper technical record.
Is it exploited?
Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is confirmed. Listed in CISA KEV.
Who is affected?
Exim.
What should we do?
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
Overview
An issue was discovered in the base64d function in the SMTP listener in Exim before 4.90.1
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.
- Published
- 08 Feb 2018
- Exploitation Reported
- 03 Nov 2021
- Attack vector
- Remote
- Complexity
- Low
- Privileges
- None
- User interaction
- None
Tags
malware
cisa
ransomware
CVE References
- CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2018-6789
- USN-3565-1 usn.ubuntu.com · Vendor Advisory https://usn.ubuntu.com/3565-1/
- DSA-4110 debian.org · Vendor Advisory https://www.debian.org/security/2018/dsa-4110
- 44571 exploit-db.com · Exploit https://www.exploit-db.com/exploits/44571/
- 45671 exploit-db.com · Exploit https://www.exploit-db.com/exploits/45671/
- 1040461 securitytracker.com · VDB Entry http://www.securitytracker.com/id/1040461
- 103049 securityfocus.com · VDB Entry http://www.securityfocus.com/bid/103049
- [oss-security] 20180207 CVE-2018-6789 Exim 4.90 and earlier: buffer overflow openwall.com · Mailing List http://www.openwall.com/lists/oss-security/2018/02/07/2
- [debian-lts-announce] 20180210 [SECURITY] [DLA 1274-1] exim4 security update lists.debian.org · Mailing List https://lists.debian.org/debian-lts-announce/2018/02/msg00009.html
- exim.org/static/doc/security/CVE-2018-6789.txt exim.org · CVE Record https://exim.org/static/doc/security/CVE-2018-6789.txt
- OSS-Security Mailing List openwall.com · CVE Record http://openwall.com/lists/oss-security/2018/02/10/2
- git.exim.org/exim.git/commit/cf3cd306062a08969c41a1cdd32c... git.exim.org · CVE Record https://git.exim.org/exim.git/commit/cf3cd306062a08969c41a1cdd32c6855...
- devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiti... devco.re · CVE Record https://devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2...
- packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.html packetstormsecurity.com · CVE Record http://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overf...
Exploitation evidence
Why Previdian marks this CVE as exploited
Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.
Exploited in the wild
CISA
A trusted third party reported exploitation.
Used in malware
CISA
Malware families have been linked to exploitation of this CVE.
Known exploited vulnerability sources
Per-source evidence links for KEV attestations are available through the Previdian Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| CISA First | 2021-11-03 00:00 UTC |
Detection
Operational artifacts and observed signals
Make the evidence actionable in scanner, SOC, and edge-control workflows.
Observed signals
- Request targets
- User-Agents
- Callback hosts
- 0
- 0
- 0
Request targets and User-Agents available in Pro. Callback host details available in Enterprise.
Scanner coverage
No scanner integrations recorded yet.
Virtual patch status
No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.
Learn about virtual patches →No detection artifacts or sensor request patterns are available for this CVE yet.
Check back as sensor telemetry and scanner integrations are updated.
Risk and context
Severity, weaknesses, and research context
CVSS v3.1
9.8
Critical
Potential damage if exploited. Separate from whether attackers are using it.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
82.1%
Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.
All CVSS Scores
CVSS v3.1
9.8
Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v2.0
7.5
High
AV:N/AC:L/Au:N/C:P/I:P/A:P
Timeline
From disclosure to observed exploitation
-
00:00 UTC
Added to CISA KEV
Listed in the CISA Known Exploited Vulnerabilities catalog
-
00:00 UTC
First public exploitation report
Exploit observed in malware
-
23:00 UTC
CVE published
Vulnerability disclosed publicly
-
00:00 UTC
CVE ID reserved
Identifier reserved by the CNA
Pro API
Automate this intelligence
Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
- Evidence confidence and provenance
- First-party sensor telemetry
- PoC and scanner references
- Affected versions and enrichment
- Automation-ready JSON delivery
GET /api/v2/pro/kevs/CVE-2018-6789
Free JSON includes basic KEV fields{
"cve_id": "CVE-2018-6789",
"confidence": "Confirmed",
"cvss_score": 9.8,
"cvss_estimated": false,
"epss_score": 0.82137,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "attempts": 0, "sensors": 0 }
}