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PatchSiren cyber security CVE debrief

CVE-2018-6789 Exim CVE debrief

CVE-2018-6789 is an Exim buffer overflow vulnerability that CISA has placed in its Known Exploited Vulnerabilities catalog. The KEV entry indicates known exploitation and also marks the issue as having known ransomware campaign use, which makes it a high-priority item for defenders even without additional product details in the source corpus.

Vendor
Exim
Product
Exim
CVSS
Unknown
CISA KEV
Listed
Original CVE published
2021-11-03
Original CVE updated
2021-11-03
Advisory published
2021-11-03
Advisory updated
2021-11-03

Who should care

Anyone running Exim, especially teams responsible for internet-facing mail servers, vulnerability management, incident response, and patch operations.

Technical summary

The supplied official sources identify CVE-2018-6789 as an Exim buffer overflow vulnerability and record it in CISA’s KEV catalog. CISA’s metadata marks the issue as known exploited and notes known ransomware campaign use. The corpus does not include version ranges, attack prerequisites, or impact specifics, so defensive action should focus on confirming whether Exim is deployed, validating exposure, and applying vendor guidance immediately.

Defensive priority

Urgent. CISA KEV inclusion and known ransomware campaign use make this a high-priority remediation item for any environment that still has Exim deployed.

Recommended defensive actions

  • Apply updates per vendor instructions for any affected Exim deployment.
  • Inventory all Exim instances, including internet-facing mail gateways and legacy systems.
  • Verify whether Exim is exposed externally and reduce exposure where possible.
  • Prioritize remediation ahead of routine maintenance because the issue is listed in CISA KEV.
  • Review mail server and host logs for unusual activity if patching has been delayed.
  • Remove, isolate, or replace unsupported Exim installations that cannot be updated promptly.

Evidence notes

CISA’s KEV source item lists vendorProject Exim, product Exim, vulnerabilityName "Exim Buffer Overflow Vulnerability," dateAdded 2021-11-03, dueDate 2022-05-03, and knownRansomwareCampaignUse "Known." The source also points to the official NVD record for CVE-2018-6789. Published and modified dates in the provided timeline are 2021-11-03; those are the KEV/source dates used here, not the CVE issue date.

Sources and references

Verified primary and authoritative sources

  • CVE-2018-6789 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2018-6789

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2018-6789 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2018-6789

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

  • CISA Known Exploited Vulnerabilities catalog

    Publisher, destination, and source semantics verified

    URL: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

    Cybersecurity and Infrastructure Security Agency - Official CISA catalog of vulnerabilities known to be exploited in the wild.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

    cisa_kev

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.