CVE-2023-51747: 
Java vulnerability analysis and mitigation

Apache James prior to versions 3.8.1 and 3.7.5 is vulnerable to SMTP smuggling (CVE-2023-51747). The vulnerability was discovered in 2023 and disclosed on February 27, 2024. The issue stems from lenient behavior in line delimiter handling that creates a difference in interpretation between sender and receiver, which can be exploited to forge SMTP envelopes (NVD, Apache List).

The vulnerability involves SMTP smuggling, where a difference in interpretation of line delimiters between sender and receiver can be exploited. The issue specifically relates to how the software handles line delimiter processing during the DATA transaction of SMTP communications. The vulnerability has been assigned a CVSS 3.1 Base Score of 7.1 (HIGH) with vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N. The vulnerability is classified under CWE-20 (Improper Input Validation), CWE-444 (Inconsistent Interpretation of HTTP Requests), and CWE-290 (Authentication Bypass by Spoofing) (NVD).

The vulnerability allows attackers to forge SMTP envelopes, which can lead to bypassing SPF (Sender Policy Framework) checks. This means attackers could potentially send emails appearing to come from legitimate domains, effectively bypassing email authentication mechanisms (SEC Consult).

Users are recommended to upgrade to Apache James versions 3.8.1 or 3.7.5 or later. The patch enforces CRLF as a line delimiter as part of the DATA transaction. No alternative workarounds have been published (Apache List).