[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$f4s49G3R9V9esH02OMPWzhiXu070pbXJB9AtZHFE0EMA":3},{"article":4,"iocs":54},{"id":5,"title":6,"slug":7,"summary":8,"ai_summary":9,"brief":10,"full_text":11,"url":12,"image_url":13,"published_at":14,"ingested_at":15,"relevance_score":16,"entities":17,"category_id":31,"category":32,"article_tags":36},"a0348277-2639-407d-b416-b28c4c375190","Cisco Patches Firewall Zero-Day Exploited for DoS Attacks","cisco-patches-firewall-zero-day-exploited-for-dos-attacks-fb25dd","CVE-2026-20349 can be exploited remotely without authentication against Secure Firewall ASA and FTD devices. The post Cisco Patches Firewall Zero-Day Exploited for DoS Attacks appeared first on SecurityWeek.","Cisco has released patches for a zero-day vulnerability, CVE-2026-20349, affecting its Secure Firewall ASA and FTD devices. The flaw allows remote, unauthenticated attackers to cause a denial-of-service (DoS) by sending a crafted HTTP request. Cisco acknowledged active exploitation in August 2026 and has urged customers to apply the patches immediately. CISA has also added the vulnerability to its Known Exploited Vulnerabilities catalog.","Cisco patches firewall zero-day (CVE-2026-20349) exploited for DoS attacks.","Cisco informed customers on Tuesday that it has released patches for a zero-day vulnerability affecting firewalls running Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) software. The security hole, tracked as CVE-2026-20349, is related to the processing of HTTP requests. A remote, unauthenticated attacker can cause an appliance to reload and enter a denial-of-service (DoS) condition by sending a specially crafted HTTP request to the Remote Access SSL VPN service. The vulnerability was discovered internally by Cisco and also reported by an external researcher. Cisco said it became aware of active exploitation in August 2026, but has not shared any information on the attacks involving CVE-2026-20349. These types of vulnerabilities could allow threat actors to disrupt security appliances, potentially preventing them from detecting and blocking further malicious activity.Advertisement. Scroll to continue reading. Cisco has urged customers to apply the available hotfixes as soon as possible. CISA added CVE-2026-20349 to its Known Exploited Vulnerabilities (KEV) catalog on Tuesday, instructing federal agencies to patch it by August 14. This is the 12th Cisco product bug with a 2026 CVE identifier added to the KEV list this year. While a majority are SD-WAN product flaws, threat actors have also exploited Unified CM and FMC vulnerabilities. Related: Cisco Warns of High-Severity ClamAV Vulnerabilities With Public PoC Related: Cisco Patches Critical SD-WAN, IOS XE, FMC Vulnerabilities Related: Microsoft Fixes 421 CVEs, One Exploited Zero-Day Written By Eduard Kovacs Eduard Kovacs (@EduardKovacs) is senior managing editor at SecurityWeek. He worked as a high school IT teacher before starting a career in journalism in 2011. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering. Daily Briefing Newsletter Subscribe to the SecurityWeek Email Briefing for the latest cybersecurity threats, trends, and expert insights. 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(Torsten George) Flipboard Reddit Whatsapp Whatsapp Email","https:\u002F\u002Fwww.securityweek.com\u002Fcisco-patches-firewall-zero-day-exploited-for-dos-attacks\u002F","https:\u002F\u002Fwww.securityweek.com\u002Fwp-content\u002Fuploads\u002F2024\u002F07\u002FCisco-switches-network.jpeg","2026-08-12T05:10:47+00:00","2026-08-12T06:00:02.253664+00:00",9,[18,21,23,26,29],{"name":19,"type":20},"Secure Firewall ASA","product",{"name":22,"type":20},"Secure Firewall FTD",{"name":24,"type":25},"Cisco","vendor",{"name":27,"type":28},"SSL VPN","technology",{"name":30,"type":28},"HTTP","80544778-fabb-4dcd-aa35-17492e5dcf4f",{"id":31,"icon":33,"name":34,"slug":35},null,"Vulnerabilities","vulnerabilities",[37,42,47,49],{"category":38},{"id":39,"icon":33,"name":40,"slug":41},"574f766a-fb3f-487c-8d2c-0720ae75471b","Zero-day","zero-day",{"category":43},{"id":44,"icon":33,"name":45,"slug":46},"6cbdd207-aaa1-4176-9534-e156b125e917","Nation-state","nation-state",{"category":48},{"id":31,"icon":33,"name":34,"slug":35},{"category":50},{"id":51,"icon":33,"name":52,"slug":53},"e7b231c8-5f79-4465-8d38-1ef13aea5a14","Threat Intelligence","threat-intelligence",[55],{"type":56,"value":57,"context":58},"cve","CVE-2026-20349","Cisco Secure Firewall ASA and FTD denial-of-service vulnerability"]