Exim flaws being used in attacks

CISA lists 5 flaws in Exim products as being used in attacks, most recently on 25 Mar 2022. 1 has been used in ransomware.

What to do

1. Update every Exim product you use.Install the updates Exim offers, on every device, and restart when asked. Each flaw below has a fix or clear advice; that’s one of CISA’s conditions for listing it.
2. If someone looks after IT for you, send them this page.Many of these are in equipment you don’t see: routers, firewalls, servers, the office network. Ask them to confirm each one is fixed, or that you don’t use the product.
3. Check anything else in the lookup.Search any app, company or CVE. Not being on CISA’s list doesn’t mean safe: keep updating either way.

Every flaw, newest first

1. Being used in attacksAdded by CISA on 25 Mar 2022
   Exim
   CVE-2010-4345Exim Privilege Escalation Vulnerability
   Exim allows local users to gain privileges by leveraging the ability of the exim user account to specify an alternate configuration file with a directive that contains arbitrary commands.
   CISA’s required actionApply updates per vendor instructions.
   CVE recordNVD
2. Being used in attacksAdded by CISA on 25 Mar 2022
   Exim
   CVE-2010-4344Exim Heap-Based Buffer Overflow Vulnerability
   Heap-based buffer overflow in the string_vformat function in string.c in Exim before 4.70 allows remote attackers to execute arbitrary code via an SMTP session.
   CISA’s required actionApply updates per vendor instructions.
   CVE recordNVD
3. Being used in attacksAdded by CISA on 3 Mar 2022
   Exim Internet Mailer
   CVE-2019-16928Exim Out-of-bounds Write Vulnerability
   Exim contains an out-of-bounds write vulnerability which can allow for remote code execution.
   CISA’s required actionApply updates per vendor instructions.
   CVE recordNVD
4. Being used in attacksAdded by CISA on 10 Jan 2022
   Exim Mail Transfer Agent (MTA)
   CVE-2019-10149Exim 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.
   CISA’s required actionApply updates per vendor instructions.
   CVE recordNVD
5. Being used in attacksUsed in ransomwareAdded by CISA on 3 Nov 2021
   Exim
   CVE-2018-6789Exim Buffer Overflow Vulnerability
   Exim contains a buffer overflow vulnerability in the base64d function part of the SMTP listener that may allow for remote code execution.
   CISA’s required actionApply updates per vendor instructions.
   CVE recordNVD

From CISA’s Known Exploited Vulnerabilities catalog, updated 21 Oct 2026 (version 2026.10.21). CISA’s required actions are written for US government agencies. Exim on CISA’s site.