CVE-2018-6789

CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score elevated to 9.8 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 9.8 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 5 sources updated this weekExploited in the wild
9.8EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 82%CVSS: 9.8Exploit: cisa kev · ssvc active · kev ransomware · epss top5pct · epss high · public exploitExposed: 0

A fix is available — apply it.

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 v3
9.8
EG Score
9.8(high)
EG Risk
99(Act)
EG Risk 99/100SSVC: Act

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation100% × 40%
Automatability100% × 15%
Action: Fix now — active exploitation, automatable, high impact.
EPSS PROB
82%
EPSS %ILE
100%
KEV
⚠ Exploited

Published

February 8, 2018

Last Modified

November 7, 2025

Advisory Details (9)

Auto-updated Sep 17, 2026
⚠️ Active exploitation confirmed. Patch available.
generic Patch Available

[SECURITY] [DLA 1274-1] exim4 security update

https://lists.debian.org/debian-lts-announce/2018/02/msg00009.html
generic

Exim Internet Mailer

https://git.exim.org/exim.git/commit/cf3cd306062a08969c41a1cdd32c6855f1abecf1
generic
https://exim.org/static/doc/security/CVE-2018-6789.txt
generic

Exim Off-by-one RCE: Exploiting CVE-2018-6789 with Fully Mitigations Bypassing | DEVCORE

https://devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2018-6789-en/
generic🔴 Active Exploitation

CVE-2018-6789 - PSIRT.COM

http://www.securityfocus.com/bid/103049
generic

oss-security - CVE-2018-6789 Exim 4.90 and earlier: buffer overflow

http://www.openwall.com/lists/oss-security/2018/02/07/2
generic

Packet Storm Security

http://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.html
generic

oss-security - Exim 4.90.1 released. (Was: CVE-2018-6789 Exim 4.90 and earlier: buffer overflow)

http://openwall.com/lists/oss-security/2018/02/10/2
generic
http://www.securitytracker.com/id/1040461

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntueximon4 (4.86.2-2ubuntu2.3) @ xenial2026-09-19ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(7 across 7 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
exim4—4.90.1-1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
exim4—4.90.1-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
exim4—4.90.1-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
exim4—4.90.1-1—
Debian:7(1)
PackageVulnerable rangeFixed inDependents
exim44.80-7 ... 4.80-7+deb7u5 (6 versions)4.80-7+deb7u6—
Debian:8(1)
PackageVulnerable rangeFixed inDependents
exim44.84-8 ... 4.84.2-2+deb8u4 (10 versions)4.84.2-2+deb8u5—
Debian:9(1)
PackageVulnerable rangeFixed inDependents
exim44.89-2, 4.89-2+deb9u1, 4.89-2+deb9u1~bpo8+1, 4.89-2+deb9u2, 4.89-2+deb9u3~bpo8+14.89-2+deb9u3—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 96× in last 7d / 383× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 1,357 total refreshes for this CVE.

  1. 2026-09-19 19:43 UTCVendor advisory
  2. 2026-09-19 19:43 UTCGHSA enrichment
  3. 2026-09-19 15:55 UTCGHSA enrichment
  4. 2026-09-19 12:05 UTCVendor advisory
  5. 2026-09-19 12:05 UTCGHSA enrichment
  6. 2026-09-19 08:18 UTCVendor advisory
  7. 2026-09-19 08:18 UTCGHSA enrichment
  8. 2026-09-19 04:30 UTCVendor advisory
  9. 2026-09-19 04:30 UTCGHSA enrichment
  10. 2026-09-19 00:43 UTCVendor advisory
  11. 2026-09-19 00:43 UTCGHSA enrichment
  12. 2026-09-18 20:55 UTCEG score recompute
  13. 2026-09-18 20:55 UTCVendor advisory
  14. 2026-09-18 20:55 UTCGHSA enrichment
  15. 2026-09-18 19:22 UTCEPSS rescore
  16. 2026-09-18 19:20 UTCCISA KEV update
  17. 2026-09-18 17:08 UTCVendor advisory
  18. 2026-09-18 17:08 UTCGHSA enrichment
  19. 2026-09-18 14:15 UTCCISA KEV update
  20. 2026-09-18 13:20 UTCVendor advisory
  21. 2026-09-18 13:20 UTCGHSA enrichment
  22. 2026-09-18 09:32 UTCVendor advisory
  23. 2026-09-18 09:32 UTCGHSA enrichment
  24. 2026-09-18 05:45 UTCVendor advisory
  25. 2026-09-18 05:45 UTCGHSA enrichment
Show 75 more
  1. 2026-09-18 01:58 UTCVendor advisory
  2. 2026-09-18 01:58 UTCGHSA enrichment
  3. 2026-09-17 22:11 UTCEG score recompute
  4. 2026-09-17 22:11 UTCVendor advisory
  5. 2026-09-17 22:11 UTCGHSA enrichment
  6. 2026-09-17 19:22 UTCEPSS rescore
  7. 2026-09-17 18:23 UTCVendor advisory
  8. 2026-09-17 18:23 UTCGHSA enrichment
  9. 2026-09-17 14:36 UTCVendor advisory
  10. 2026-09-17 14:36 UTCGHSA enrichment
  11. 2026-09-17 10:49 UTCVendor advisory
  12. 2026-09-17 10:49 UTCGHSA enrichment
  13. 2026-09-17 07:02 UTCVendor advisory
  14. 2026-09-17 07:02 UTCGHSA enrichment
  15. 2026-09-17 03:15 UTCVendor advisory
  16. 2026-09-17 03:15 UTCGHSA enrichment
  17. 2026-09-16 23:28 UTCVendor advisory
  18. 2026-09-16 23:28 UTCGHSA enrichment
  19. 2026-09-16 19:40 UTCVendor advisory
  20. 2026-09-16 19:40 UTCGHSA enrichment
  21. 2026-09-16 15:53 UTCEG score recompute
  22. 2026-09-16 15:53 UTCVendor advisory
  23. 2026-09-16 15:53 UTCGHSA enrichment
  24. 2026-09-16 14:10 UTCCISA KEV update
  25. 2026-09-16 12:06 UTCVendor advisory
  26. 2026-09-16 12:05 UTCGHSA enrichment
  27. 2026-09-16 08:18 UTCGHSA enrichment
  28. 2026-09-16 04:28 UTCVendor advisory
  29. 2026-09-16 04:28 UTCGHSA enrichment
  30. 2026-09-16 00:41 UTCVendor advisory
  31. 2026-09-16 00:41 UTCGHSA enrichment
  32. 2026-09-15 20:53 UTCVendor advisory
  33. 2026-09-15 20:53 UTCGHSA enrichment
  34. 2026-09-15 17:05 UTCVendor advisory
  35. 2026-09-15 17:05 UTCGHSA enrichment
  36. 2026-09-15 13:18 UTCVendor advisory
  37. 2026-09-15 13:18 UTCGHSA enrichment
  38. 2026-09-15 09:31 UTCVendor advisory
  39. 2026-09-15 09:31 UTCGHSA enrichment
  40. 2026-09-15 05:43 UTCEG score recompute
  41. 2026-09-15 05:43 UTCVendor advisory
  42. 2026-09-15 05:43 UTCGHSA enrichment
  43. 2026-09-15 03:05 UTCEPSS rescore
  44. 2026-09-15 03:05 UTCEPSS rescore
  45. 2026-09-15 01:55 UTCVendor advisory
  46. 2026-09-15 01:55 UTCGHSA enrichment
  47. 2026-09-14 22:07 UTCGHSA enrichment
  48. 2026-09-14 19:24 UTCCISA KEV update
  49. 2026-09-14 18:19 UTCGHSA enrichment
  50. 2026-09-14 14:31 UTCVendor advisory
  51. 2026-09-14 14:31 UTCGHSA enrichment
  52. 2026-09-14 10:44 UTCVendor advisory
  53. 2026-09-14 10:44 UTCGHSA enrichment
  54. 2026-09-14 06:56 UTCVendor advisory
  55. 2026-09-14 06:56 UTCGHSA enrichment
  56. 2026-09-14 03:09 UTCVendor advisory
  57. 2026-09-14 03:09 UTCGHSA enrichment
  58. 2026-09-13 23:22 UTCVendor advisory
  59. 2026-09-13 23:22 UTCGHSA enrichment
  60. 2026-09-13 19:35 UTCVendor advisory
  61. 2026-09-13 19:35 UTCGHSA enrichment
  62. 2026-09-13 15:47 UTCVendor advisory
  63. 2026-09-13 15:47 UTCGHSA enrichment
  64. 2026-09-13 12:00 UTCVendor advisory
  65. 2026-09-13 12:00 UTCGHSA enrichment
  66. 2026-09-13 08:12 UTCVendor advisory
  67. 2026-09-13 08:12 UTCGHSA enrichment
  68. 2026-09-13 04:25 UTCVendor advisory
  69. 2026-09-13 04:25 UTCGHSA enrichment
  70. 2026-09-13 00:37 UTCVendor advisory
  71. 2026-09-13 00:37 UTCGHSA enrichment
  72. 2026-09-12 20:49 UTCVendor advisory
  73. 2026-09-12 20:49 UTCGHSA enrichment
  74. 2026-09-12 17:01 UTCVendor advisory
  75. 2026-09-12 17:01 UTCGHSA enrichment

Publicly available exploits

(6 references)

Working exploit code is in the public domain (4 GitHub PoCs) (2 Exploit-DB entries). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCthistehneisen/CVE-2018-6789-Python3
    First seen Aug 5, 2023

    Exim < 4.90.1 RCE Vulnerability remake for Python3 with arguments passed from CLI

    Open source ↗
  • GitHub PoCmartinclauss/exim-rce-cve-2018-6789
    First seen Mar 2, 2020

    This repository provides a learning environment to understand how an Exim RCE exploit for CVE-2018-6789 works.

    Open source ↗
  • GitHub PoCsynacktiv/Exim-CVE-2018-6789
    First seen Oct 10, 2019

    PoC materials to exploit CVE-2018-6789

    Open source ↗
  • GitHub PoCberaphin/CVE-2018-6789
    First seen Nov 8, 2018
    Open source ↗
  • Exploit-DBEDB-45671
    First seen Oct 24, 2018

    exim 4.90 - Remote Code Execution

    Open source ↗
  • Exploit-DBEDB-44571
    First seen May 2, 2018

    Exim < 4.90.1 - 'base64d' Remote Code Execution

    Open source ↗

Frequently asked(6)

What is CVE-2018-6789?
CVE-2018-6789 is a critical vulnerability published on February 8, 2018. 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.
When was CVE-2018-6789 disclosed?
CVE-2018-6789 was first published in the National Vulnerability Database on February 8, 2018, with the most recent update on November 7, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2018-6789 actively exploited?
Yes. CISA added CVE-2018-6789 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting Exim Exim. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2018-6789?
CVE-2018-6789 has a CVSS v3 base score of 9.8 (NVD).
Which products are affected by CVE-2018-6789?
CVE-2018-6789 affects Exim Exim. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2018-6789?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2018-6789, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2018-6789

Explore →

Is Your Infrastructure Affected by CVE-2018-6789?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs