{"id":257020,"date":"2026-05-23T07:00:00","date_gmt":"2026-05-23T11:00:00","guid":{"rendered":"https:\/\/news-you-need.com\/index.php\/2026\/05\/23\/underminr-vulnerability-lets-attackers-hide-malicious-connections-behind-trusted-domains\/"},"modified":"2026-05-27T13:05:23","modified_gmt":"2026-05-27T17:05:23","slug":"underminr-vulnerability-lets-attackers-hide-malicious-connections-behind-trusted-domains","status":"publish","type":"post","link":"https:\/\/news-you-need.com\/index.php\/2026\/05\/23\/underminr-vulnerability-lets-attackers-hide-malicious-connections-behind-trusted-domains\/","title":{"rendered":"\u2018Underminr\u2019 Vulnerability Lets Attackers Hide Malicious Connections Behind Trusted Domains"},"content":{"rendered":"<p><a href=\"https:\/\/www.securityweek.com\/underminr-vulnerability-lets-attackers-hide-malicious-connections-behind-trusted-domains\/\">\u2018Underminr\u2019 Vulnerability Lets Attackers Hide Malicious Connections Behind Trusted Domains<\/a><\/p>\n<p><a href=\"https:\/\/www.securityweek.com\/underminr-vulnerability-lets-attackers-hide-malicious-connections-behind-trusted-domains\/\">https:\/\/www.securityweek.com\/underminr-vulnerability-lets-attackers-hide-malicious-connections-behind-trusted-domains\/<\/a><\/p>\n<p>Publish Date: <a href=\"publish_date]\">2026-05-23 07:00:00<\/a><\/p>\n<p>Source Domain: <a href=\"www.securityweek.com\">www.securityweek.com<\/a><\/p>\n<p class=\"wp-block-paragraph\"><strong>Threat actors are exploiting a vulnerability in shared content delivery network (CDN) infrastructure to hide connections to malicious domains.<\/strong><\/p>\n<p class=\"wp-block-paragraph\">Dubbed Underminr, the issue is a variant of domain fronting, a now-mitigated type of attack that enabled threat actors to place an allowed domain in the SNI and TLS certificate validation fields of an HTTPS request, while embedding a different target domain in the TLS tunnel\u2019s encrypted HTTP host header.<\/p>\n<p class=\"wp-block-paragraph\">Because CDNs routed requests internally based on the host headers, the request reached the hidden destination, while traffic would appear to be going to a reputable front domain.<\/p>\n<p class=\"wp-block-paragraph\">Instead of using a front domain, Underminr presents the SNI and HTTP Host of a domain while forcing a request to the IP address of another tenant on the same shared edge.<\/p>\n<p class=\"wp-block-paragraph\">The mismatch, ADAMnetworks reports, has been exploited in attacks targeting large-scale hosting providers, including those that have implemented mitigations against domain fronting.<\/p>\n<p class=\"wp-block-paragraph\">\u201cThis abuse permits connections that appear to go to a trusted domain to actually connect to another domain that could be used for malicious intent,\u201d the web security firm explains.<\/p>\n<p><span class=\"zox-ad-label\">Advertisement. Scroll to continue reading.<\/span><\/p>\n<p class=\"wp-block-paragraph\">Threat actors can abuse Underminr to hide connections to command-and-control (C&#038;C) servers, as well as VPN and proxy connections, and to circumvent network egress policies.<\/p>\n<p class=\"wp-block-paragraph\">\u201cIn the simple form, the detection gap appears when DNS decisions, edge IPs, SNI, Host headers, and CDN tenant routing are not correlated. The endpoint sees an allowed DNS lookup while the connection can complete against a different hosted name,\u201d ADAMnetworks says.<\/p>\n<p class=\"wp-block-paragraph\">According to the company, the attack technique has been abused in attacks to connect to domains hosted on CDN infrastructure shared with allowed domains, mostly via TCP connections on port 443, in which SNI exposes the intended TLS hostname.<\/p>\n<p class=\"wp-block-paragraph\">The Underminr vulnerability can be exploited using four different&#8230;<\/p>\n<p><a href=\"https:\/\/www.securityweek.com\/underminr-vulnerability-lets-attackers-hide-malicious-connections-behind-trusted-domains\/\">Source<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u2018Underminr\u2019 Vulnerability Lets Attackers Hide Malicious Connections Behind Trusted Domains https:\/\/www.securityweek.com\/underminr-vulnerability-lets-attackers-hide-malicious-connections-behind-trusted-domains\/ Publish Date: 2026-05-23 07:00:00&#8230;<\/p>\n","protected":false},"author":1,"featured_media":257021,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"fifu_image_url":"https:\/\/www.securityweek.com\/wp-content\/uploads\/2026\/05\/Underminr-DNS-vulnerability.jpg","fifu_image_alt":"","footnotes":""},"categories":[15],"tags":[27],"class_list":["post-257020","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cybersecurity","tag-vulnerability"],"_links":{"self":[{"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/posts\/257020"}],"collection":[{"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/comments?post=257020"}],"version-history":[{"count":1,"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/posts\/257020\/revisions"}],"predecessor-version":[{"id":257022,"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/posts\/257020\/revisions\/257022"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/media\/257021"}],"wp:attachment":[{"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/media?parent=257020"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/categories?post=257020"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/news-you-need.com\/index.php\/wp-json\/wp\/v2\/tags?post=257020"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}