{"id":86805,"date":"2026-03-29T12:55:03","date_gmt":"2026-03-29T12:55:03","guid":{"rendered":""},"modified":"-0001-11-30T00:00:00","modified_gmt":"-0001-11-30T06:00:00","slug":"cve-2025-51986-infinite-loop-vulnerability-in-freemodbus-v-2018-09-12","status":"publish","type":"post","link":"https:\/\/www.ameeba.com\/blog\/cve-2025-51986-infinite-loop-vulnerability-in-freemodbus-v-2018-09-12\/","title":{"rendered":"<strong>CVE-2025-51986: Infinite Loop Vulnerability in freemodbus v.2018-09-12<\/strong>"},"content":{"rendered":"<p><strong>Overview<\/strong><\/p>\n<p>The vulnerability CVE-2025-51986 is a critical cybersecurity issue discovered in the demo\/LINUXTCP implementation of cwalter-at freemodbus v.2018-09-12. This vulnerability can allow attackers to trigger an infinite loop in the system via a crafted packet length value. The vulnerability primarily affects users or systems utilizing the said freemodbus component and poses a significant risk due to its potential for system compromise and data leakage.<\/p>\n<p><strong>Vulnerability Summary<\/strong><\/p>\n<p>CVE ID: CVE-2025-51986<br \/>\nSeverity: High (7.5 CVSS score)<br \/>\nAttack Vector: Network<br \/>\nPrivileges Required: None<br \/>\nUser Interaction: None<br \/>\nImpact: Potential system compromise and data leakage<\/p>\n<p><strong>Affected Products<\/strong><\/p><div id=\"ameeb-2496829664\" 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: 700px;\">\r\n  <h2 style=\"margin-top: 0; font-size: 20px; font-weight: 600; display: flex; align-items: center;\">\r\n    <a href=\"https:\/\/www.ameeba.com\/chat\" style=\"display: inline-flex; align-items: center; margin-right: 8px;\">\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: 40px; height: 40px;\" \/>\r\n    <\/a>\r\n    A new way to communicate\r\n  <\/h2>\r\n\r\n  <p style=\"margin-bottom: 12px;\">\r\n    Ameeba Chat is built on encrypted identity, not personal profiles.\r\n  <\/p>\r\n\r\n  <p style=\"margin-bottom: 16px;\">\r\n    Message, call, share files, and coordinate with identities kept separate.\r\n  <\/p>\r\n\r\n  <ul style=\"list-style: none; padding-left: 0; margin-bottom: 20px;\">\r\n    <li>\u2022 Encrypted identity<\/li>\r\n    <li>\u2022 Ameeba Chat authenticates access<\/li>\r\n    <li>\u2022 Aliases and categories<\/li>\r\n    <li>\u2022 End-to-end encrypted chat, calls, and files<\/li>\r\n    <li>\u2022 Secure notes for sensitive information<\/li>\r\n  <\/ul>\r\n\r\n  <p style=\"font-style: italic; font-weight: 600; margin-bottom: 24px;\">\r\n    Private communication, rethought.\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: 6px; font-weight: 500;\">Download Ameeba Chat<\/a>\r\n    <a href=\"https:\/\/www.ameeba.com\/chat\" style=\"border: 1px solid #ffffff; color: #ffffff; padding: 10px 20px; text-decoration: none; border-radius: 6px; font-weight: 500;\">Learn More<\/a>\r\n  <\/div>\r\n<\/div>\r\n<\/div>\n<p>Product | Affected Versions<\/p>\n<p>freemodbus | v.2018-09-12<\/p>\n<p><strong>How the Exploit Works<\/strong><\/p>\n<p>The exploit works by crafting a packet with a specific length value that could trigger an infinite loop in the demo\/LINUXTCP implementation of freemodbus. This loop can cause system instability, potentially leading to system compromise or data leakage.<\/p>\n<p><strong>Conceptual Example Code<\/strong><\/p><div id=\"ameeb-4180353467\" 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 represents a crafted packet with a malicious length value that could trigger the infinite loop.<\/p>\n<pre><code class=\"\" data-line=\"\">POST \/LINUXTCP\/freemodbus HTTP\/1.1\nHost: target.example.com\nContent-Type: application\/mbap\n{ &quot;transaction_identifier&quot;: &quot;1234&quot;, &quot;protocol_identifier&quot;: &quot;00&quot;, &quot;length&quot;: &quot;infinite&quot;, &quot;unit_identifier&quot;: &quot;01&quot; }<\/code><\/pre>\n<p><strong>Mitigation<\/strong><\/p>\n<p>To mitigate this vulnerability, users are advised to apply the vendor-provided patch as soon as it&#8217;s available. In the meantime, users could employ Web Application Firewalls (WAF) or Intrusion Detection Systems (IDS) as temporary mitigation strategies. These tools can help detect and block malicious packets, preventing attackers from exploiting this vulnerability.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Overview The vulnerability CVE-2025-51986 is a critical cybersecurity issue discovered in the demo\/LINUXTCP implementation of cwalter-at freemodbus v.2018-09-12. This vulnerability can allow attackers to trigger an infinite loop in the system via a crafted packet length value. The vulnerability primarily affects users or systems utilizing the said freemodbus component and poses a significant risk due [&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-86805","post","type-post","status-publish","format-standard","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/86805","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=86805"}],"version-history":[{"count":0,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/86805\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/media?parent=86805"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/categories?post=86805"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/tags?post=86805"},{"taxonomy":"vendor","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/vendor?post=86805"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/product?post=86805"},{"taxonomy":"attack_vector","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/attack_vector?post=86805"},{"taxonomy":"asset_type","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/asset_type?post=86805"},{"taxonomy":"severity","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/severity?post=86805"},{"taxonomy":"exploit_status","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/exploit_status?post=86805"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}