New Critical Exim Flaw Exposes Email Servers to Remote Attacks — Patch Released

A critical protection vulnerability has been uncovered and set in the well-liked open up-source Exim e-mail server software program, which could make it possible for a distant attacker to only crash or perhaps execute malicious code on targeted servers.

Exim maintainers currently unveiled an urgent stability update—Exim version 4.92.3—after publishing an early warning two days back, giving process directors an early head-up on its impending security patches that have an impact on all versions of the e mail server computer software from 4.92 up to and together with then-most up-to-date version 4.92.2.

Exim is a extensively used, open source mail transfer agent (MTA) created for Unix-like running programs like Linux, Mac OSX or Solaris, which runs virtually 60 % of the Internet’s e mail servers nowadays for routing, providing and getting e-mail messages.

This is the second time in this thirty day period when the Exim maintainers have unveiled an urgent safety update. Before this month, the team patched a vital remote code execution flaw (CVE-2019-15846) in the software that could have authorized remote attackers to achieve root-stage obtain to the technique.

Discovered as CVE-2019-16928 and discovered by Jeremy Harris of Exim Enhancement Group, the vulnerability is a heap-primarily based buffer overflow (memory corruption) situation in string_vformat described in string.c file of the EHLO Command Handler element.

The stability flaw could permit remote attackers to lead to a denial of assistance (DoS) problem or execute arbitrary code on a qualified Exim mail server using a specially crafted line in the EHLO command with the legal rights of the focused person.

According to the Exim advisory, a at the moment identified PoC exploit for this vulnerability makes it possible for one particular to only crash the Exim process by sending a very long string in the EHLO command, though other instructions could also be applied to perhaps execute arbitrary code.

“The at this time regarded exploit employs an extraordinary long EHLO string to crash the Exim process that is acquiring the concept,” says the Exim developers’ group.

“Even though at this method of procedure, Exim already dropped its privileges, other paths to get to the vulnerable code might exist.”

In mid-year, Exim also patched a extreme remote command execution vulnerability (CVE-2019-10149) in its email program that was actively exploited in the wild by different teams of hackers to compromise vulnerable servers.

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For that reason, server administrators are hugely suggested to install the newest Exim 4.92.3 version as before long as doable, since there is no known mitigation to quickly take care of this situation.

The staff also says, “if you cannot set up the above versions, talk to your package maintainer for a model containing the backported correct. On ask for and depending on our sources, we will support you in backporting the take care of.”

The stability update is offered for Linux distributions, which includes Ubuntu, Arch Linux, FreeBSD, Debian, and Fedora.

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