{"id":87091,"date":"2026-06-10T18:54:21","date_gmt":"2026-06-10T18:54:21","guid":{"rendered":""},"modified":"-0001-11-30T00:00:00","modified_gmt":"-0001-11-30T00:00:00","slug":"cve-2025-61600-unbounded-memory-allocation-vulnerability-in-stalwart-mail-server","status":"publish","type":"post","link":"https:\/\/www.ameeba.com\/blog\/cve-2025-61600-unbounded-memory-allocation-vulnerability-in-stalwart-mail-server\/","title":{"rendered":"CVE-2025-61600: Unbounded Memory Allocation Vulnerability in Stalwart Mail Server<\/strong>"},"content":{"rendered":"

Overview<\/strong><\/p>\n

The Stalwart mail and collaboration server is facing a potential cyber threat. A critical vulnerability, CVE-2025-61600, has been identified in versions 0.13.3 and below. This vulnerability could allow a remote attacker to exhaust the server’s memory, potentially risking a system compromise or data leakage. Hence, it is vital for organizations using the Stalwart server to take immediate action to mitigate this risk.<\/p>\n

Vulnerability Summary<\/strong><\/p>\n

CVE ID: CVE-2025-61600
\nSeverity: High (7.5 CVSS score)
\nAttack Vector: Network
\nPrivileges Required: None
\nUser Interaction: None
\nImpact: Potential system compromise or data leakage due to server memory exhaustion<\/p>\n

Affected Products<\/strong><\/p>\n

Product | Affected Versions<\/p>\n

Stalwart Mail Server | 0.13.3 and below<\/p>\n

How the Exploit Works<\/strong><\/p>\n

The vulnerability resides in the IMAP protocol parser of the Stalwart server. The CommandParser implementation enforces size limits on its dynamic buffer in most parsing states, but there are several state handlers that omit these validation checks. This omission leads to an unbounded memory allocation issue, enabling a remote attacker to send specific requests that can exhaust the server’s memory. This potential exhaustion could trigger the system’s out-of-memory (OOM) killer, causing a denial of service.<\/p>\n

Conceptual Example Code<\/strong><\/p>\n

Below is a conceptual example of how the vulnerability might be exploited. This pseudocode could be part of a script that continuously sends requests to the server without proper size validation checks, leading to memory exhaustion.<\/p>\n

while (true) {\nPOST \/imap\/protocol HTTP\/1.1\nHost: target.example.com\nContent-Type: application\/json\n{ \"large_size_request\": \"A\"*1000000000 }\n}<\/code><\/pre>\n
Mitigation Guidance<\/strong><\/p>\n
The immediate solution is to update the Stalwart server to version 0.13.4, where the issue is fixed. Alternatively, you can implement rate limiting and connection monitoring at the network level as a workaround. However, this does not provide complete protection. For temporary mitigation, using a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) can help until the vendor patch is applied.<\/p>\n","protected":false},"excerpt":{"rendered":"
Overview The Stalwart mail and collaboration server is facing a potential cyber threat. A critical vulnerability, CVE-2025-61600, has been identified in versions 0.13.3 and below. This vulnerability could allow a remote attacker to exhaust the server’s memory, potentially risking a system compromise or data leakage. Hence, it is vital for organizations using the Stalwart server […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[],"tags":[],"vendor":[],"product":[],"attack_vector":[],"asset_type":[],"severity":[],"exploit_status":[],"class_list":["post-87091","post","type-post","status-publish","format-standard","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t