Overview
Recently, NSFOCUS CERT detected an Exim remote code execution vulnerability (CVE-2023-42115). When external authentication is enabled, due to improper user input verification, an unauthenticated attacker can remotely exploit this vulnerability by writing data beyond the bounds, ultimately executing arbitrary code on the target server. At present, the details of the vulnerability have been disclosed. Affected users should take measures as soon as possible.
Scope of Impact
Affected version
- Exim4<4.96.1
Unaffected version
- Exim4>=4.96.1
Mitigation
Official upgrade
At present, Exim has officially released a security version to fix this vulnerability. It is recommended that affected users upgrade the version as soon as possible for protection: https://ftp.exim.org/pub/exim/exim4/
Temporary mitigation
Turn off external authentication and execute the exim4- bP config command. If driver=external in the output, it indicates that external authentication is enabled and needs to be turned off.
Statement
This advisory is only used to describe a potential risk. NSFOCUS does not provide any commitment or promise on this advisory. NSFOCUS and the author will not bear any liability for any direct and/or indirect consequences and losses caused by transmitting and/or using this advisory. NSFOCUS reserves all the rights to modify and interpret this advisory. Please include this statement paragraph when reproducing or transferring this advisory. Do not modify this advisory, add/delete any information to/from it, or use this advisory for commercial purposes without permission from NSFOCUS.
About NSFOCUS
NSFOCUS, Inc., a global network and cyber security leader, protects enterprises and carriers from advanced cyberattacks. The company’s Intelligent Hybrid Security strategy utilizes both cloud and on-premises security platforms, built on a foundation of real-time global threat intelligence, to provide multi-layered, unified and dynamic protection against advanced cyber attacks.
NSFOCUS works with Fortune Global 500 companies, including four of the world’s five largest financial institutions, organizations in insurance, retail, healthcare, critical infrastructure industries as well as government agencies. NSFOCUS has technology and channel partners in more than 60 countries, is a member of both the Microsoft Active Protections Program (MAPP), and the Cloud Security Alliance (CSA). A wholly owned subsidiary of NSFOCUS Technologies Group Co., Ltd., the company has operations in the Americas, Europe, the Middle East and Asia Pacific.
