{"id":34699,"date":"2025-05-05T15:13:07","date_gmt":"2025-05-05T15:13:07","guid":{"rendered":""},"modified":"2025-10-29T04:22:10","modified_gmt":"2025-10-29T10:22:10","slug":"cve-2023-35704-critical-buffer-overflow-vulnerabilities-in-gtkwave-s-fst-leb128-varint-functionality","status":"publish","type":"post","link":"https:\/\/www.ameeba.com\/blog\/cve-2023-35704-critical-buffer-overflow-vulnerabilities-in-gtkwave-s-fst-leb128-varint-functionality\/","title":{"rendered":"<strong>CVE-2023-35704: Critical Buffer Overflow Vulnerabilities in GTKWave&#8217;s FST LEB128 Varint Functionality<\/strong>"},"content":{"rendered":"<p><strong>Overview<\/strong><\/p>\n<p>The cybersecurity landscape is constantly evolving, with new vulnerabilities being discovered on a regular basis. One such vulnerability is the CVE-2023-35704, a serious security flaw identified in the GTKWave 3.3.115. This vulnerability is particularly concerning as it affects the <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2023-34436-critical-out-of-bounds-write-vulnerability-in-gtkwave-3-3-115\/\"  data-wpil-monitor-id=\"41039\">FST LEB128 varint<\/a> functionality of GTKWave, a widely used waveform viewer for Verilog RTL simulation.<br \/>\nThe flaw is significant due to its potential to enable an attacker to execute arbitrary code, <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-32857-sql-injection-vulnerability-in-telecontrol-server-basic-leading-to-potential-system-compromise\/\"  data-wpil-monitor-id=\"39753\">leading to full system compromise or potential<\/a> data leakage. This could have <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-40566-severe-user-session-vulnerability-in-simatic-pcs-neo-products\/\"  data-wpil-monitor-id=\"48866\">severe implications for users<\/a>, particularly those in industries where data security is paramount. As such, understanding this <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-31637-high-risk-sql-injection-vulnerability-in-lambertgroup-shout\/\"  data-wpil-monitor-id=\"51878\">vulnerability and how to mitigate its risks<\/a> is of the utmost importance.<\/p>\n<p><strong>Vulnerability Summary<\/strong><\/p>\n<p>CVE ID: CVE-2023-35704<br \/>\nSeverity: High (7.8 CVSS Score)<br \/>\nAttack Vector: File-based (<a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-32701-elevation-of-privileges-via-windows-common-log-file-system-driver\/\"  data-wpil-monitor-id=\"91782\">via a specially crafted .fst file)<\/a><br \/>\nPrivileges Required: None<br \/>\nUser Interaction: Required (victim needs to open the malicious file)<br \/>\nImpact: <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2023-43958-arbitrary-file-upload-vulnerability-in-hospital-management-system-v4-0\/\"  data-wpil-monitor-id=\"39695\">Arbitrary code execution leading to system<\/a> compromise or data leakage<\/p>\n<p><strong>Affected Products<\/strong><\/p><div id=\"ameeb-2703246801\" 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>GTKWave | 3.3.115<\/p>\n<p><strong>How the Exploit Works<\/strong><\/p>\n<p>The exploit takes advantage of multiple stack-based <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-28024-buffer-overflow-vulnerability-in-totolink-a810r-v4-1-2cu-5182-b20201026\/\"  data-wpil-monitor-id=\"39565\">buffer overflow vulnerabilities<\/a> in the FST LEB128 varint functionality of GTKWave 3.3.115. An attacker crafts a malicious .fst file which, when opened by the victim, overflows the buffer, allowing the attacker to <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2024-40446-arbitrary-code-execution-vulnerability-in-forkosh-mime-tex\/\"  data-wpil-monitor-id=\"39853\">execute arbitrary code<\/a> on the victim&#8217;s system. This is achieved through the manipulation of the fstReaderVarint32WithSkip function, which fails to properly handle specially crafted .fst files.<\/p>\n<p><strong>Conceptual Example Code<\/strong><\/p><div id=\"ameeb-136804020\" 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>Here&#8217;s a conceptual example of how the <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-47154-exploitation-of-use-after-free-vulnerability-in-libjs-in-ladybird\/\"  data-wpil-monitor-id=\"48867\">vulnerability might be exploited<\/a>. This is a simplified representation and actual exploit code may be more complex.<\/p>\n<pre><code class=\"\" data-line=\"\">#include &lt;stdio.h&gt;\n#include &lt;string.h&gt;\nvoid malicious_fst_file() {\nchar buffer[10];\n\/\/ a crafted .fst file with contents exceeding the buffer size\nchar *malicious_fst = &quot;Exceedingly_long_and_malicious_file_content...&quot;;\nstrcpy(buffer, malicious_fst);\n}\nint main() {\nmalicious_fst_file();\nreturn 0;\n}<\/code><\/pre>\n<p>In this example, the `malicious_fst` string represents the malicious .fst file. When the `malicious_fst_file` function is executed, the buffer overflows due to the excessive length of the malicious .fst file, potentially leading to <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-45428-remote-arbitrary-code-execution-vulnerability-in-tenda-ac9-v1-0-firmware\/\"  data-wpil-monitor-id=\"40043\">arbitrary code execution<\/a>.<\/p>\n<p><strong>Mitigation Guidance<\/strong><\/p>\n<p>As a preventive measure, users are advised to apply the vendor patch as soon as it is available. This patch will fix the <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2023-35004-critical-integer-overflow-vulnerability-in-gtkwave-3-3-115\/\"  data-wpil-monitor-id=\"41060\">vulnerabilities present in the FST LEB128 varint functionality of GTKWave<\/a> 3.3.115. In the interim, using a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) can serve as temporary mitigation, providing some level of protection against <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=\"40178\">potential attacks exploiting this vulnerability<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Overview The cybersecurity landscape is constantly evolving, with new vulnerabilities being discovered on a regular basis. One such vulnerability is the CVE-2023-35704, a serious security flaw identified in the GTKWave 3.3.115. This vulnerability is particularly concerning as it affects the FST LEB128 varint functionality of GTKWave, a widely used waveform viewer for Verilog RTL simulation. [&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":[86,80],"asset_type":[],"severity":[],"exploit_status":[],"class_list":["post-34699","post","type-post","status-publish","format-standard","hentry","category-uncategorized","attack_vector-buffer-overflow","attack_vector-rce"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/34699","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=34699"}],"version-history":[{"count":11,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/34699\/revisions"}],"predecessor-version":[{"id":84955,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/34699\/revisions\/84955"}],"wp:attachment":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/media?parent=34699"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/categories?post=34699"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/tags?post=34699"},{"taxonomy":"vendor","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/vendor?post=34699"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/product?post=34699"},{"taxonomy":"attack_vector","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/attack_vector?post=34699"},{"taxonomy":"asset_type","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/asset_type?post=34699"},{"taxonomy":"severity","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/severity?post=34699"},{"taxonomy":"exploit_status","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/exploit_status?post=34699"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}