+44 1865 950 828 Secure Your Business
Actively exploited

CVE-2019-10149 Exim Mail Transfer Agent (MTA) Improper Input Validation

Improper validation of recipient address in deliver_message() function in /src/deliver.c may lead to remote command execution.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 10 Jan 2022.
  • Rated Critical severity (CVSS 9.0, scored by Vendor).
  • It has been in the catalogue for 1,761 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

A flaw was found in Exim versions 4.87 to 4.91 (inclusive). Improper validation of recipient address in deliver_message() function in /src/deliver.c may lead to remote command execution.

Affected Versions

ProductVersions
exim exim4.92

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Exim Mail Transfer Agent (MTA). Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated critical, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 10 Jul 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Exim Flaws

Get alerts for EximWe email you when a new Exim vulnerability is confirmed as exploited. Add more vendors on Threat Watch.

By signing up you agree to receive Threat Watch alerts. Unsubscribe at any time. See our Privacy Policy.

CVE-2010-4345Exim Privilege Escalation VulnerabilityAdded 25 Mar 2022CVE-2010-4344Exim Heap-Based Buffer Overflow VulnerabilityAdded 25 Mar 2022CVE-2019-16928Exim Out-of-bounds Write VulnerabilityAdded 3 Mar 2022CVE-2018-6789 · RansomwareExim Buffer Overflow VulnerabilityAdded 3 Nov 2021

All 5 exploited Exim vulnerabilities

Not Sure If You Are Exposed?

Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2019-10149 and every other exploited flaw on the list.

Check My Exposure
Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2019-10149
  3. CVE record: CVE-2019-10149
  4. FIRST EPSS
  5. openwall.com/lists/oss-security/2019/06/05/2
  6. usn.ubuntu.com/4010-1/
  7. openwall.com/lists/oss-security/2019/06/05/3
  8. openwall.com/lists/oss-security/2019/06/05/4
  9. debian.org/security/2019/dsa-4456
  10. seclists.org/bugtraq/2019/Jun/5
  11. security.gentoo.org/glsa/201906-01
  12. openwall.com/lists/oss-security/2019/06/06/1