{"id":86449,"date":"2026-02-12T19:17:03","date_gmt":"2026-02-12T19:17:03","guid":{"rendered":""},"modified":"-0001-11-30T00:00:00","modified_gmt":"-0001-11-30T06:00:00","slug":"cve-2025-5399-high-severity-dos-vulnerability-in-libcurl-s-websocket-code","status":"publish","type":"post","link":"https:\/\/www.ameeba.com\/blog\/cve-2025-5399-high-severity-dos-vulnerability-in-libcurl-s-websocket-code\/","title":{"rendered":"<strong>CVE-2025-5399: High Severity DoS Vulnerability in Libcurl&#8217;s WebSocket Code<\/strong>"},"content":{"rendered":"<p><strong>Overview<\/strong><\/p>\n<p>This report discusses the recent discovery of a high-severity vulnerability, designated as CVE-2025-5399, which affects the libcurl&#8217;s WebSocket code. If exploited, this vulnerability allows a malicious server to trap libcurl in an endless busy-loop, potentially leading to a Denial-of-Service (DoS) attack. This vulnerability is of critical concern to any applications or systems using libcurl, due to the potential for data leakage or system compromise.<\/p>\n<p><strong>Vulnerability Summary<\/strong><\/p>\n<p>CVE ID: CVE-2025-5399<br \/>\nSeverity: High (CVSS 7.5)<br \/>\nAttack Vector: Network<br \/>\nPrivileges Required: None<br \/>\nUser Interaction: None<br \/>\nImpact: Denial of service leading to potential system compromise or data leakage<\/p>\n<p><strong>Affected Products<\/strong><\/p><div id=\"ameeb-2376799310\" 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>libcurl | All versions prior to patch<\/p>\n<p><strong>How the Exploit Works<\/strong><\/p>\n<p>The exploit takes advantage of a flaw in the WebSocket code of libcurl. By sending a specially crafted packet, a malicious server can cause libcurl to enter an endless busy-loop. This loop cannot be exited by the application unless the process or thread is forcibly terminated. In effect, this can lead to a DoS attack, where the application becomes unresponsive and inaccessible.<\/p>\n<p><strong>Conceptual Example Code<\/strong><\/p><div id=\"ameeb-4124880893\" 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>While we don&#8217;t have the exact exploit code, a conceptual attack might involve a WebSocket handshake request with a malicious payload. This could look something like:<\/p>\n<pre><code class=\"\" data-line=\"\">GET \/chat HTTP\/1.1\nHost: target.example.com\nUpgrade: websocket\nConnection: Upgrade\nSec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==\nSec-WebSocket-Protocol: chat, superchat\nSec-WebSocket-Version: 13\nOrigin: http:\/\/example.com\n{ &quot;malicious_payload&quot;: &quot;...&quot; }<\/code><\/pre>\n<p>In the above example, the &#8220;malicious_payload&#8221; could be the specially crafted packet which triggers the endless loop in libcurl.<\/p>\n<p><strong>Mitigation<\/strong><\/p>\n<p>As a mitigation measure, users are advised to apply the vendor patch as soon as it becomes available. Until then, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) may help to identify and block malicious packets. However, these are temporary measures and cannot completely secure the system from the vulnerability.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Overview This report discusses the recent discovery of a high-severity vulnerability, designated as CVE-2025-5399, which affects the libcurl&#8217;s WebSocket code. If exploited, this vulnerability allows a malicious server to trap libcurl in an endless busy-loop, potentially leading to a Denial-of-Service (DoS) attack. This vulnerability is of critical concern to any applications or systems using libcurl, [&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-86449","post","type-post","status-publish","format-standard","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/86449","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=86449"}],"version-history":[{"count":0,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/86449\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/media?parent=86449"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/categories?post=86449"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/tags?post=86449"},{"taxonomy":"vendor","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/vendor?post=86449"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/product?post=86449"},{"taxonomy":"attack_vector","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/attack_vector?post=86449"},{"taxonomy":"asset_type","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/asset_type?post=86449"},{"taxonomy":"severity","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/severity?post=86449"},{"taxonomy":"exploit_status","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/exploit_status?post=86449"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}