New Critical Security Flaws Expose Exim Mail Servers to Remote Attacks

Several security vulnerabilities have been disclosed in the Exim mail transfer agent that, if effectively exploited, could end result in data disclosure and distant code execution.

The list of flaws, which had been documented anonymously way back again in June 2022, is as follows –

• CVE-2023-42114 (CVSS score: 3.7) – Exim NTLM Challenge Out-Of-Bounds Go through Information and facts Disclosure Vulnerability
• CVE-2023-42115 (CVSS score: 9.8) – Exim AUTH Out-Of-Bounds Publish Distant Code Execution Vulnerability
• CVE-2023-42116 (CVSS score: 8.1) – Exim SMTP Challenge Stack-centered Buffer Overflow Distant Code Execution Vulnerability
• CVE-2023-42117 (CVSS rating: 8.1) – Exim Inappropriate Neutralization of Exclusive Components Distant Code Execution Vulnerability
• CVE-2023-42118 (CVSS score: 7.5) – Exim libspf2 Integer Underflow Remote Code Execution Vulnerability
• CVE-2023-42119 (CVSS score: 3.1) – Exim dnsdb Out-Of-Bounds Read through Information Disclosure Vulnerability

The most serious of the vulnerabilities is CVE-2023-42115, which enables distant, unauthenticated attackers to execute arbitrary code on affected installations of Exim.

“The unique flaw exists in just the SMTP assistance, which listens on TCP port 25 by default,” the Zero Working day Initiative reported in an inform revealed this week.

“The issue effects from the lack of good validation of user-supplied facts, which can result in a produce previous the finish of a buffer. An attacker can leverage this vulnerability to execute code in the context of the assistance account.”

Exim maintainers, in a message shared on the Open Resource Security mailing listing oss-security, said fixes for CVE-2023-42114, CVE-2023-42115, and CVE-2023-42116 are “offered in a protected repository and are ready to be used by the distribution maintainers.”

“The remaining issues are debatable or skip details we will need to correct them,” adding it requested ZDI additional particulars about the issues and that it “failed to get responses we had been equipped to perform with” until eventually May perhaps 2023. The Exim crew additional reported they are awaiting specific specifics on the other three shortcomings.

However, the ZDI pushed back again versus statements about “sloppy dealing with” and “neither staff pinging the other for 10 months,” stating it attained out various occasions to the developers.

“Just after our disclosure timeline was exceeded by numerous months, we notified the maintainer of our intent to publicly disclose these bugs, at which time we have been informed, ‘you do what you do,'” it claimed.

“If these bugs have been appropriately dealt with, we will update our advisories with a backlink to the security advisory, code test-in, or other general public documentation closing the issue.”

In the absence of patches, the ZDI endorses restricting conversation with the application as the only “salient” mitigation approach.

This is not the 1st time security flaws have been uncovered in the commonly employed mail transfer agent. In May well 2021, Qualys disclosed a established of 21 vulnerabilities collectively tracked as 21Nails that allow unauthenticated attackers to attain total distant code execution and achieve root privileges.

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Beforehand in Might 2020, the U.S. federal government reported that hackers affiliated with Sandworm, a condition-sponsored group from Russia, had been exploiting a critical Exim vulnerability (CVE-2019-10149, CVSS rating: 9.8) to penetrate delicate networks.

The improvement also comes scorching on the heels of a new research by researchers from the College of California San Diego that identified a novel strategy known as forwarding-primarily based spoofing which can take gain of weaknesses in email forwarding to send messages impersonating legit entities, thus compromising on integrity.

“The primary protocol utilised to verify the authenticity of an email implicitly assumes that just about every organization operates its possess mailing infrastructure, with precise IP addresses not employed by other domains,” the investigate located.

“But currently, quite a few corporations outsource their email infrastructure to Gmail and Outlook. As a final result, thousands of domains have delegated the appropriate to deliver email on their behalf to the identical 3rd social gathering. Though these 3rd-social gathering providers validate that their users only send email on behalf of domains that they run, this security can be bypassed by email forwarding.”

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Some parts of this article are sourced from:
thehackernews.com