{"id":34110,"date":"2025-05-01T16:35:25","date_gmt":"2025-05-01T16:35:25","guid":{"rendered":""},"modified":"2025-06-09T23:20:22","modified_gmt":"2025-06-10T05:20:22","slug":"cve-2021-47663-unauthenticated-remote-attacker-gaining-full-access-due-to-improper-json-web-tokens-implementation","status":"publish","type":"post","link":"https:\/\/www.ameeba.com\/blog\/cve-2021-47663-unauthenticated-remote-attacker-gaining-full-access-due-to-improper-json-web-tokens-implementation\/","title":{"rendered":"<strong>CVE-2021-47663: Unauthenticated Remote Attacker Gaining Full Access Due to Improper JSON Web Tokens Implementation<\/strong>"},"content":{"rendered":"<p><strong>Overview<\/strong><\/p>\n<p>CVE-2021-47663 is a critical vulnerability that enables an unauthenticated remote attacker to guess a valid session ID, allowing them to impersonate a user and gain full access to the system. With the rise of remote work and digital spaces, the security of online systems is paramount. This <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-43949-high-risk-sql-injection-vulnerability-in-mum-mapedit-web-application\/\"  data-wpil-monitor-id=\"39547\">vulnerability affects any system that has improperly implemented JSON Web<\/a> Tokens, posing a significant threat to data integrity and system security. The <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-1290-high-severity-race-condition-use-after-free-vulnerability-in-kernel-5-4-on-chromeos\/\"  data-wpil-monitor-id=\"41792\">severity of the vulnerability<\/a> is underscored by its CVSS severity score of 8.1, which points to its potential for serious damage if left unaddressed.<\/p>\n<p><strong>Vulnerability Summary<\/strong><\/p>\n<p>CVE ID: CVE-2021-47663<br \/>\nSeverity: Critical (CVSS: 8.1)<br \/>\nAttack Vector: Network<br \/>\nPrivileges Required: None<br \/>\nUser Interaction: None<br \/>\nImpact: <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-22636-cross-site-scripting-vulnerability-in-vr-frases-leads-to-potential-system-compromise\/\"  data-wpil-monitor-id=\"40216\">System compromise and potential<\/a> data leakage<\/p>\n<p><strong>Affected Products<\/strong><\/p><div id=\"ameeb-1075826142\" 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>[Product 1] | [All versions with improper JWT implementation]<br \/>\n[Product 2] | [All versions with improper JWT implementation]<\/p>\n<p><strong>How the Exploit Works<\/strong><\/p>\n<p>The <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2024-49563-improper-neutralization-exploit-in-dell-unity-leads-to-privilege-escalation\/\"  data-wpil-monitor-id=\"56771\">exploit takes advantage of an improper<\/a> implementation of JSON Web Tokens (JWTs). JWTs are an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. This information can be verified and trusted because it is digitally signed. However, if the JWTs are implemented improperly, the digital signature can be compromised.<br \/>\nAn attacker can use this <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-45953-session-hijacking-vulnerability-in-phpgurukul-hostel-management-system\/\"  data-wpil-monitor-id=\"41186\">vulnerability to guess a valid session<\/a> ID. Once the session ID is guessed, it allows the attacker to impersonate a user, which in turn grants them full <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-45746-unauthorized-system-access-via-hardcoded-jwt-secret-in-zkt-zkbio-cvsecurity\/\"  data-wpil-monitor-id=\"48916\">access to the system<\/a>. This can <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-32849-vulnerability-in-telecontrol-server-basic-leads-to-potential-system-compromise\/\"  data-wpil-monitor-id=\"39548\">lead to system compromise or potential<\/a> data leakage, putting sensitive data at risk.<\/p>\n<p><strong>Conceptual Example Code<\/strong><\/p><div id=\"ameeb-1381535620\" 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>A potential exploit might look something like this, where the attacker sends a malicious <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-47462-cross-site-request-forgery-vulnerability-in-ohidul-islam-challan-leading-to-privilege-escalation\/\"  data-wpil-monitor-id=\"43694\">request to a vulnerable<\/a> endpoint:<\/p>\n<pre><code class=\"\" data-line=\"\">POST \/vulnerable\/endpoint HTTP\/1.1\nHost: target.example.com\nContent-Type: application\/json\n{ &quot;session_id&quot;: &quot;guessed_or_stolen_session_id&quot; }<\/code><\/pre>\n<p>In this conceptual example, the &#8220;guessed_or_stolen_session_id&#8221; represents a session ID that the attacker has either guessed or stolen, <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-31478-zulip-server-vulnerability-allowing-unauthorized-account-creation\/\"  data-wpil-monitor-id=\"40325\">allowing them to impersonate a user and gain unauthorized<\/a> access to the system.<\/p>\n<p><strong>Mitigation<\/strong><\/p>\n<p>To mitigate this vulnerability, apply the patch provided by the vendor as soon as possible. If a patch is not immediately available or cannot be applied immediately, use a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) as a temporary measure to detect and prevent exploitation attempts. Additionally, ensure that <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-49151-unauthenticated-attackers-can-forge-json-web-tokens-in-microsens-nmp-web\/\"  data-wpil-monitor-id=\"64541\">JSON Web Tokens<\/a> are properly implemented as per the guidelines in RFC 7519.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Overview CVE-2021-47663 is a critical vulnerability that enables an unauthenticated remote attacker to guess a valid session ID, allowing them to impersonate a user and gain full access to the system. With the rise of remote work and digital spaces, the security of online systems is paramount. This vulnerability affects any system that has improperly [&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":[1],"tags":[],"vendor":[],"product":[],"attack_vector":[],"asset_type":[],"severity":[],"exploit_status":[],"class_list":["post-34110","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/34110","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=34110"}],"version-history":[{"count":9,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/34110\/revisions"}],"predecessor-version":[{"id":58045,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/34110\/revisions\/58045"}],"wp:attachment":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/media?parent=34110"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/categories?post=34110"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/tags?post=34110"},{"taxonomy":"vendor","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/vendor?post=34110"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/product?post=34110"},{"taxonomy":"attack_vector","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/attack_vector?post=34110"},{"taxonomy":"asset_type","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/asset_type?post=34110"},{"taxonomy":"severity","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/severity?post=34110"},{"taxonomy":"exploit_status","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/exploit_status?post=34110"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}