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Findings

CVE-2018-6789

Exim Buffer Overflow Vulnerability

Published Feb 8, 2018 · corrected/updated Jun 16, 2026 · exim exim · evidence confidence very high

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.

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2018-6789 is a critical public vulnerability record for exim exim. CISA lists it as known exploited. Published remediation guidance: Apply updates per vendor instructions. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether exim exim is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: canonical/ubuntu linux (14.04); canonical/ubuntu linux (16.04); canonical/ubuntu linux (17.10); debian/debian linux (7.0). Published remediation guidance: Apply updates per vendor instructions. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: CVSS 9.8, EPSS 82.1%. CISA lists it as known exploited. Weakness classes: CWE-119, CWE-120. Sources contributing to this record: cisa_kev, cve_org, epss, exploitdb. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

  • Exploitation evidence

    Confirmed in CISA KEV since Nov 3, 2021. Listed in the CISA Known Exploited Vulnerabilities catalog.

  • Patch and remediation

    Apply updates per vendor instructions. CISA due date May 3, 2022.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 8, 2018 · Catalog

    Detected

    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.

  2. Nov 3, 2021 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. May 3, 2022 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Jun 16, 2026 · Catalog

    Updated

    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.

Affected

  • cpe canonical/ubuntu linux14.04
  • cpe canonical/ubuntu linux16.04
  • cpe canonical/ubuntu linux17.10
  • cpe debian/debian linux7.0
  • cpe debian/debian linux8.0
  • cpe debian/debian linux9.0
  • cpe exim/eximversion unspecified
  • vendor Exim Eximversion unspecified

Sources

  • CISA KEVConfirmed exploitationCVE-2018-6789

    Exim contains a buffer overflow vulnerability in the base64d function part of the SMTP listener that may allow for remote code execution.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2018-6789

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2018-6789

    30-day exploitation probability 82.1%

    first.org
  • Exploit DatabasePublic exploit reference44571

    Public archive entry. The exploit body is not stored here.

    exploit-db.com
  • Exploit DatabasePublic exploit reference45671

    Public archive entry. The exploit body is not stored here.

    exploit-db.com
  • NIST NVDVulnerability recordCVE-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.

    nvd.nist.gov
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com

References