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Cisco has disclosed and patched CVE-2026-20349, a high-severity zero-day in Cisco Secure Firewall ASA and Secure Firewall Threat Defense (FTD) that is being actively exploited to trigger denial-of-service conditions. The flaw is caused by insufficient error checking when processing HTTP requests in the Remote Access SSL VPN service, allowing a remote, unauthenticated attacker to crash and reload affected devices. Impacted deployments include systems with SSL listen sockets enabled, such as SSL VPN, IKEv2 Remote Access VPN with client services, and Zero Trust Network Access on FTD devices, while Secure Firewall Management Center is not affected.
Cisco released fixed software and hotfixes for multiple ASA and FTD versions and said there is no workaround other than upgrading. CISA added the bug to its Known Exploited Vulnerabilities catalog, alongside newly listed flaws in Microsoft Windows and Metabase, and directed federal agencies to remediate the Cisco issue by August 14, 2026 under BOD 26-04. Cisco said it became aware of exploitation in August but did not identify the threat actor, targets, or indicators of compromise.
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3 events from the most recent confirmed update back to the earliest known activity.
On 2026-08-11, CISA added CVE-2026-20349 to its Known Exploited Vulnerabilities catalog, identifying it as affecting Cisco Secure Firewall ASA and FTD and noting that exploitation can cause device reload and denial of service. CISA set a remediation due date of August 14, 2026 for federal agencies.
Cisco PSIRT said it became aware in August 2026 that CVE-2026-20349, a denial-of-service flaw in Cisco Secure Firewall ASA and FTD, was being actively exploited in the wild. Cisco did not disclose the threat actor, targets, or indicators of compromise.
Cisco disclosed CVE-2026-20349 as a high-severity flaw in Secure Firewall ASA and FTD that can be exploited remotely without authentication via crafted HTTP requests to the Remote Access SSL VPN service, causing device reloads and denial of service. Cisco released hotfixes for affected ASA and FTD versions and said there are no workarounds beyond upgrading to fixed releases.
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Cisco has disclosed multiple critical zero-day vulnerabilities affecting its Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Software, which are actively being exploited in the wild. The vulnerabilities, tracked as CVE-2025-20362 and CVE-2025-20333, impact the VPN web server component of these devices and can lead to remote code execution or unauthorized access. According to Cisco's advisory, CVE-2025-20362 allows unauthenticated, remote attackers to access restricted URL endpoints without authentication by sending specially crafted HTTP requests. CVE-2025-20333, on the other hand, enables authenticated attackers with valid VPN credentials to execute arbitrary code as root, potentially resulting in full device compromise. CISA has responded by adding both vulnerabilities to its Known Exploited Vulnerabilities Catalog and issuing an emergency directive (ED 25-03) that requires federal agencies to identify, analyze, and mitigate any potential compromises immediately. The vulnerabilities stem from improper validation of user-supplied input in HTTP(S) requests, making it possible for attackers to bypass security controls. Cisco has provided a list of vulnerable configurations, including those using AnyConnect IKEv2 Remote Access with client services enabled. The CVE-2025-20333 vulnerability is rated as critical with a CVSS score of 9.9, underscoring the severity of the threat. Exploitation of these flaws could allow attackers to gain root-level access, execute arbitrary code, and take full control of affected devices. The vulnerabilities affect a wide range of Cisco products, including ASA, FTD, and potentially IOS, IOS XE, and IOS XR software, as described in related advisories. Cisco has urged all customers to apply patches immediately to prevent exploitation. The vulnerabilities are being actively targeted, increasing the urgency for organizations to remediate affected systems. Attackers exploiting these flaws could use compromised devices as entry points into broader enterprise networks. The technical details highlight the importance of proper input validation in web services exposed to the internet. Organizations are advised to review their firewall configurations and ensure that all relevant updates are applied. The rapid response from CISA and Cisco reflects the high risk posed by these vulnerabilities to both public and private sector networks. Security teams should monitor for signs of compromise and follow Cisco's mitigation guidance to reduce exposure. The incident demonstrates the ongoing threat posed by zero-day vulnerabilities in widely deployed network security appliances.
Jun 29, 2026
Cisco confirmed that multiple government agencies engaged its incident response teams in May 2025 to investigate targeted attacks against Cisco Adaptive Security Appliance (ASA) 5500-X Series devices running Cisco Secure Firewall ASA Software with VPN web services enabled. Attackers exploited multiple zero-day vulnerabilities to implant malware, execute commands, and potentially exfiltrate data from compromised devices. The threat actor demonstrated advanced evasion techniques, including disabling logging, intercepting CLI commands, and intentionally crashing devices to hinder forensic analysis. Cisco’s investigation, which involved providing instrumented images and analyzing packet captures and firmware, led to the identification of a critical memory corruption bug in the ASA software. The company assessed with high confidence that the activity was linked to the same threat actor behind the ArcaneDoor campaign previously reported in 2024. While the vulnerable software is present on other hardware platforms and in Cisco Secure Firewall Threat Defense (FTD) Software, there is no evidence of successful compromise beyond the ASA 5500-X Series. Cisco published detailed detection guidance, highlighting that the threat actor continues to scan for vulnerable devices using frequently changing IP addresses, and that scanning activity alone does not indicate compromise. Only specific ASA 5500-X models running certain software releases with VPN web services enabled have been confirmed as compromised. The threat actor suppressed specific syslog messages in memory as a forensic countermeasure, and a downward shift in these logs may indicate malicious activity. On September 25, 2025, Cisco released security advisories addressing critical vulnerabilities, including CVE-2025-20333, CVE-2025-20362, and CVE-2025-20363, affecting a range of ASA and FTD software versions. The Canadian Centre for Cyber Security issued alerts urging organizations to review Cisco’s advisories, apply mitigations, and update affected devices. The vulnerabilities allow for remote code execution and unauthorized access via VPN web services and HTTP servers on affected firewall products. Cisco’s advisories provided a comprehensive list of affected software versions and recommended immediate action to mitigate risk. The incident underscores the sophistication of the threat actor, the importance of timely patching, and the need for enhanced monitoring of VPN-enabled firewall devices. Cisco’s response included collaboration with affected customers, deployment of enhanced detection capabilities, and ongoing monitoring for further malicious activity. Organizations are advised to follow Cisco’s guidance, monitor for suppressed syslog IDs, and engage Cisco Technical Assistance Center if compromise is suspected. The campaign highlights the persistent targeting of network edge devices by advanced threat actors and the criticality of maintaining up-to-date security controls.
Jun 29, 2026
Multiple critical vulnerabilities have been discovered in the Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) WebVPN components, which are being actively exploited in the wild. The vulnerabilities, identified as CVE-2025-20362, CVE-2025-20333, and CVE-2025-20363, allow attackers to bypass authentication and achieve remote code execution (RCE) as root on affected devices. CVE-2025-20362 is an unauthenticated authorization bypass that enables attackers to access restricted endpoints without valid credentials, serving as a key component in exploit chains. When combined with CVE-2025-20333, attackers can send malicious HTTPS requests to execute arbitrary code as root, even without prior authentication. CVE-2025-20363 is a related flaw that also enables unauthenticated RCE on ASA/FTD devices and authenticated RCE on some Cisco IOS components. These vulnerabilities affect Cisco ASA versions 9.16 through 9.23 and Cisco FTD versions 7.0 through 7.7, with specific software images requiring validation against Cisco advisories. Cisco and CISA have confirmed active exploitation and widespread scanning for these vulnerabilities, prompting CISA to issue Emergency Directive 25-03 on September 25, 2025, mandating immediate action by federal agencies. The threat actor responsible for these attacks is attributed to the same group behind the ArcaneDoor (UAT4356) state-sponsored espionage campaign first observed in 2024. Organizations are urged to patch or upgrade to Cisco’s fixed releases without delay, and to restrict or disable vulnerable devices if immediate upgrades are not possible. Compromised devices should be isolated and thoroughly investigated for signs of threat actor presence. Cisco has provided detailed guidance for detection, and CISA’s Malware Next Generation tool can be used to hunt for indicators of compromise. Security researchers, including Rapid7, have published technical analyses and exploit chains demonstrating the severity and ease of exploitation. The vulnerabilities are considered highly critical due to their unauthenticated nature and the potential for full device compromise, which could lead to further lateral movement within affected networks. The rapid response from both Cisco and CISA underscores the urgency and scale of the threat. Organizations using Cisco ASA or FTD devices should assume exposure if running affected versions and prioritize remediation. The vulnerabilities highlight the ongoing targeting of network edge devices by sophisticated threat actors, particularly those engaged in espionage. Failure to address these vulnerabilities could result in significant operational disruption and data compromise. The security community continues to monitor for new exploitation techniques and advises ongoing vigilance. The release of proof-of-concept code and active scanning increases the risk of opportunistic attacks by additional threat actors. Timely patching and adherence to Cisco and CISA recommendations are essential to mitigate risk from these critical vulnerabilities.
Jun 29, 2026