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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.
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13 events from the most recent confirmed update back to the earliest known activity.
CISA disclosed that a U.S. federal civilian agency's Cisco Firepower device running ASA software had been compromised in September 2025 with the FIRESTARTER backdoor, which remained on the device even after patches were applied. CISA and the UK NCSC said FIRESTARTER is part of a broader campaign exploiting CVE-2025-20333 and CVE-2025-20362 and warned that patching alone may not remove the malware from already compromised systems.
Cisco published a new security advisory describing the continued evolution of a persistence mechanism used against Secure Firewall ASA and FTD devices. The advisory indicates attackers refined post-compromise persistence beyond the techniques previously documented in 2025, adding new technical detail for defenders.
By early October 2025, threat research reports said attackers were chaining the Cisco flaws with brute-force activity, disabling logging, installing backdoors, and in some cases modifying firmware, underscoring the severity of compromise and recovery challenges.
By September 30 and October 1, 2025, multiple outlets reported that nearly 50,000 Cisco firewalls were still vulnerable despite active exploitation warnings and available fixes, showing limited patch uptake and ongoing risk.
As of September 29, 2025, Shadowserver scans identified more than 48,800 internet-exposed Cisco ASA and FTD appliances that remained vulnerable, with the largest concentration in the United States.
On 2025-09-26, Finland’s National Cyber Security Centre warned about the actively exploited Cisco ASA and FTD vulnerabilities and said it had already contacted hundreds of domestic organizations that may be running affected versions. The notice urged rapid patching and investigation for compromise, noting some attacks deploy persistence that can survive patching.
The UK NCSC reported that attackers exploiting the Cisco devices were deploying a shellcode loader called Line Viper followed by a GRUB bootkit named RayInitiator, adding technical detail on post-exploitation activity.
Following disclosure of the active exploitation, CISA issued an emergency directive requiring FCEB agencies to check for compromise and rapidly upgrade affected Cisco devices. The directive also required end-of-support ASA devices to be disconnected by the end of the month.
On September 26, 2025, CERT-EU published advisory 2025-036 warning about critical vulnerabilities in Cisco ASA and FTD and urging affected organizations to remediate quickly.
Cisco published fixes and related detection guidance for the ASA and FTD vulnerabilities, with reporting noting exploitation had begun before patches were available. Advisories urged rapid upgrading because the flaws could enable unauthenticated access and arbitrary code execution.
On September 25, 2025, Cisco and multiple security advisories disclosed critical vulnerabilities affecting Cisco ASA and FTD, including CVE-2025-20333 and CVE-2025-20362, and stated they were being exploited in the wild.
On September 4, 2025, GreyNoise warned that the observed Cisco ASA scanning could be tied to emerging or undocumented vulnerabilities, raising early concern before public patching guidance was available.
GreyNoise reported suspicious scanning activity targeting Cisco ASA devices in late August 2025, indicating possible reconnaissance or early exploitation activity against yet-undisclosed flaws.
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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
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 zero-day vulnerabilities have been exploited in Cisco security products, targeting both email security appliances and network firewalls. A China-linked APT, identified as UAT-9686, exploited a zero-day vulnerability (CVE-2025-20393) in Cisco email security appliances running AsyncOS, specifically when the Spam Quarantine feature is internet-accessible. This flaw allows attackers to gain root privileges, posing a severe risk to organizations relying on these appliances for email protection. In parallel, Cisco Secure Firewall Adaptive Security Appliance (ASA) and Threat Defense (FTD) software have been targeted by a separate espionage campaign, linked to the ArcaneDoor threat actor, exploiting multiple zero-days (CVE-2025-20333, CVE-2025-20362, CVE-2025-20363) to achieve unauthenticated remote code execution and persistent access, even after system reboots or upgrades. These campaigns have prompted emergency directives from CISA and highlight the ongoing threat to perimeter network devices. Attackers have leveraged these vulnerabilities to establish persistent footholds, manipulate device memory, and potentially pivot deeper into victim networks. The vulnerabilities affecting ASA and FTD firewalls were publicly disclosed and patched, but the email security appliance zero-day remains unpatched, increasing the urgency for organizations to review their exposure and apply mitigations where possible.
Jun 29, 2026