SEPTEMBER 17, 2026
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Case File

CVE-2026-33263

MEDIUM · CVSS 4.3 EPSS 0.29% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-08-28 · Last synced 2026-09-17

CyberRota Analysis

AI-Generated

The vulnerability affects the submission-login process when the mail_max_userip_connections setting is reached, leading to potential crashes due to file descriptor handling issues. This can result in users being unable to send messages or, in some cases, duplicate messages being sent, particularly in high-performance mode. Organizations using affected products, especially those in high-security or high-performance environments, should prioritize applying updates to mitigate this issue.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
exploit

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-33263
Severity
MEDIUM
CVSS
4.3
EPSS
0.29%

Original NVD Description

When mail_max_userip_connections is set (default 10) and reached, submission-login can crash with epoll() panic caused by file descriptor handling issues. If running in high-security mode (default for community releases), only the new submission connection gets terminated. If running in high-performance mode (default for Pro releases), all connections handled by the submission-login process will be terminated. The crashes can cause failure for user to send a message, or it can cause duplicate messages to be sent. If TLS is not used (in the backend server processing the submission), duplicate deliveries cannot happen, because the crash can only happen at AUTH stage. Limit the number of connections handled by single submission-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.