{"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":"-0001-11-30T06:00:00","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":"<strong>CVE-2025-61600: Unbounded Memory Allocation Vulnerability in Stalwart Mail Server<\/strong>"},"content":{"rendered":"<p><strong>Overview<\/strong><\/p>\n<p>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&#8217;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<p><strong>Vulnerability Summary<\/strong><\/p>\n<p>CVE ID: CVE-2025-61600<br \/>\nSeverity: High (7.5 CVSS score)<br \/>\nAttack Vector: Network<br \/>\nPrivileges Required: None<br \/>\nUser Interaction: None<br \/>\nImpact: Potential system compromise or data leakage due to server memory exhaustion<\/p>\n<p><strong>Affected Products<\/strong><\/p><div id=\"ameeb-3322744972\" class=\"ameeb-content-2 ameeb-entity-placement\"><div style=\"border-left: 4px solid #555; padding-left: 20px; margin: 48px 0; font-family: Roboto, sans-serif; color: #ffffff; line-height: 1.6; max-width: 720px;\">\r\n  <h2 style=\"margin-top: 0; font-size: 22px; font-weight: 600; display: flex; align-items: center; letter-spacing: -0.02em;\">\r\n    <a href=\"https:\/\/www.ameeba.com\/chat\" style=\"display: inline-flex; align-items: center; margin-right: 10px;\">\r\n      <img decoding=\"async\" src=\"https:\/\/www.ameeba.com\/blog\/wp-content\/uploads\/2025\/10\/Best-App-icon-Ameeba.png\" alt=\"Ameeba Chat Icon\" style=\"width: 42px; height: 42px;\" \/>\r\n    <\/a>\r\n    Share secrets securely\r\n  <\/h2>\r\n\r\n  <p style=\"margin-bottom: 14px; color: #d1d5db;\">\r\n    Ameeba is private infrastructure for communication and sensitive work built on encrypted identity instead of exposed corporate identity systems.\r\n  <\/p>\r\n\r\n  <p style=\"margin-bottom: 18px; color: #a1a1aa;\">\r\n    Passwords, credentials, confidential files, screenshots, internal discussions, sensitive AI context, and private coordination should not become exposed across ordinary communication platforms.\r\n  <\/p>\r\n\r\n  <ul style=\"list-style: none; padding-left: 0; margin-bottom: 24px; color: #e4e4e7;\">\r\n    <li style=\"margin-bottom: 8px;\">\u2022 Encrypted identity<\/li>\r\n    <li style=\"margin-bottom: 8px;\">\u2022 Private Spaces for organizations and teams<\/li>\r\n    <li style=\"margin-bottom: 8px;\">\u2022 End-to-end encrypted chat, calls, files, and notes<\/li>\r\n    <li style=\"margin-bottom: 8px;\">\u2022 Sensitive AI work and protected collaboration<\/li>\r\n    <li>\u2022 Built for information that cannot leak<\/li>\r\n  <\/ul>\r\n\r\n  <p style=\"font-style: italic; font-weight: 600; margin-bottom: 24px; color: #ffffff;\">\r\n    Our mission is to secure human work alongside AI.\r\n  <\/p>\r\n\r\n  <div style=\"display: flex; flex-wrap: wrap; gap: 12px;\">\r\n    <a href=\"https:\/\/www.ameeba.com\/chat\/download\" style=\"background-color: #ffffff; color: #000000; padding: 10px 20px; text-decoration: none; border-radius: 8px; font-weight: 500;\">\r\n      Download Ameeba\r\n    <\/a>\r\n\r\n    <a href=\"https:\/\/www.ameeba.com\/chat\" style=\"border: 1px solid #ffffff; color: #ffffff; padding: 10px 20px; text-decoration: none; border-radius: 8px; font-weight: 500;\">\r\n      Learn More\r\n    <\/a>\r\n  <\/div>\r\n<\/div><\/div>\n<p>Product | Affected Versions<\/p>\n<p>Stalwart Mail Server | 0.13.3 and below<\/p>\n<p><strong>How the Exploit Works<\/strong><\/p>\n<p>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&#8217;s memory. This potential exhaustion could trigger the system&#8217;s out-of-memory (OOM) killer, causing a denial of service.<\/p>\n<p><strong>Conceptual Example Code<\/strong><\/p><div id=\"ameeb-124213733\" class=\"ameeb-content ameeb-entity-placement\"><div class=\"poptin-embedded\" data-id=\"f6b387694f681\"><\/div>\r\n\r\n\r\n\r\n\r\n\r\n<\/div>\n<p>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<pre><code class=\"\" data-line=\"\">while (true) {\nPOST \/imap\/protocol HTTP\/1.1\nHost: target.example.com\nContent-Type: application\/json\n{ &quot;large_size_request&quot;: &quot;A&quot;*1000000000 }\n}<\/code><\/pre>\n<p><strong>Mitigation Guidance<\/strong><\/p>\n<p>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":"<p>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&#8217;s memory, potentially risking a system compromise or data leakage. Hence, it is vital for organizations using the Stalwart server [&hellip;]<\/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,"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":[],"_links":{"self":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/87091","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/comments?post=87091"}],"version-history":[{"count":0,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/87091\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/media?parent=87091"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/categories?post=87091"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/tags?post=87091"},{"taxonomy":"vendor","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/vendor?post=87091"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/product?post=87091"},{"taxonomy":"attack_vector","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/attack_vector?post=87091"},{"taxonomy":"asset_type","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/asset_type?post=87091"},{"taxonomy":"severity","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/severity?post=87091"},{"taxonomy":"exploit_status","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/exploit_status?post=87091"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}