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.
A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. Federal agencies are required to remediate by 2022-07-10 under CISA BOD 22-01.
This is a OS Command Injection (CWE-78) vulnerability in Exim Mail Transfer Agent (MTA). 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. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.
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Phishing link
🖼
Malicious file
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Server compromised
Probably yes if any of these apply:
Active exploitation documented in the wild. Threat-research write-up: http://packetstormsecurity.com/files/153218/Exim-4.9.1-Remote-Command-Execution.html
Manual remediation steps
Apply the Vendor Patch
This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.
CISA required action: Apply updates per vendor instructions.
References
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References