SB2022082219 - Multiple vulnerabilities in Exim

Description

This security bulletin contains information about 2 secuirty vulnerabilities.

1) Heap-based buffer overflow (CVE-ID: CVE-2022-37452)

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to a boundary error for the alias list within the host_name_lookup() function in host.c when the sender_host_name is set. A remote attacker can initiate a connection to the affected server, trigger a heap-based buffer overflow and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

2) Man-in-the-Middle (MitM) attack (CVE-ID: CVE-2021-38371)

The vulnerability allows a remote attacker to perform MitM attack.

The vulnerability exists due to the way Exim handles concurrent STARTTLS sessions when sending out emails. A malicious server can send a response to the *next* command within the existing STARTTLS sessions and force the Exim to treat this session as trusted.

Remediation

Install update from vendor's website.

References

• https://www.exim.org/static/doc/security/
• https://github.com/ivd38/exim_overflow
• https://www.openwall.com/lists/oss-security/2022/08/06/8
• https://github.com/Exim/exim/commit/d4bc023436e4cce7c23c5f8bb5199e178b4cc743
• https://github.com/Exim/exim/wiki/EximSecurity
• https://github.com/Exim/exim/compare/exim-4.94...exim-4.95
• https://www.exim.org
• https://nostarttls.secvuln.info
• https://www.exim.org/static/doc/security/CVE-2021-38371.txt