Urgent: Cisco ASA Zero-Day Duo Under Attack; CISA Triggers Emergency Mitigation Directive
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2025-20333 +1 in the same advisory: …20362 | Authenticated Buffer Overflow RCE in Cisco ASA/FTD VPN Web Server CVE-2025-20333 is a buffer overflow (CWE-120) in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) software, caused by improper validation of user-supplied input in HTTP(S) requests. An attacker who already holds valid VPN user credentials can trigger it by sending crafted HTTP(S) requests to the device's VPN web interface; the flaw is remotely exploitable over the network with low attack complexity and no user interaction. A successful exploit allows arbitrary code execution as root, possibly resulting in complete compromise of the firewall or VPN gateway. Any organization running Cisco ASA or FTD software with the VPN web server enabled is affected. Exploitation is confirmed in the wild: the CVE was added to CISA's KEV on 2025-09-25, EPSS assigns a 70.7% probability of exploitation within 30 days (99th percentile), and Cisco and the UK NCSC have warned of real-world attacks (including RayInitiator and LINE VIPER malware deployment) that chain this flaw with at least one companion Cisco vulnerability. Do: Inventory all ASA/FTD devices with the VPN web server reachable by users (especially internet-exposed ones) and upgrade to the fixed releases listed in the Cisco PSIRT advisory; where patching is delayed, apply Cisco's recommended mitigations and hunt for indicators of the reported attack chain (RayInitiator/LINE VIPER). Because exploitation requires valid VPN credentials, treat VPN user credentials on affected gateways as potentially compromised and force resets. US federal agencies must follow the mitigation steps in CISA Emergency Directive 25-03 and BOD 22-01 timelines for this KEV entry. | 9.9 group max | 71% | KEV |
| mass≈100,000–300,000 internet-exposed ASA/FTD VPN web servers (order of magnitude), within a multi-million-device installed base serving large VPN user populations |
Full article452 words · extracted from thehackernews.com · click to collapse
Ravie LakshmananSep 25, 2025Zero-Day / Vulnerability
Cisco is urging customers to patch two security flaws impacting the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software, which it said have been exploited in the wild.
The zero-day vulnerabilities in question are listed below -
- CVE-2025-20333 (CVSS score: 9.9) - An improper validation of user-supplied input in HTTP(S) requests vulnerability that could allow an authenticated, remote attacker with valid VPN user credentials to execute arbitrary code as root on an affected device by sending crafted HTTP requests
- CVE-2025-20362 (CVSS score: 6.5) - An improper validation of user-supplied input in HTTP(S) requests vulnerability that could allow an unauthenticated, remote attacker to access restricted URL endpoints without authentication by sending crafted HTTP requests
Cisco said it's aware of "attempted exploitation" of both vulnerabilities, but did not reveal who may be behind it, or how widespread the attacks are. It's suspected that the two vulnerabilities are being chained to bypass authentication and execute malicious code on susceptible appliances.
It also credited the Australian Signals Directorate, Australian Cyber Security Centre (ACSC), Canadian Centre for Cyber Security, U.K. National Cyber Security Centre (NCSC), and U.S. Cybersecurity and Infrastructure Security Agency (CISA) for supporting the investigation.
CISA Issues Emergency Directive ED 25-03
In a separate alert, CISA said it's issuing an emergency directive urging federal agencies to identify, analyze, and mitigate potential compromises with immediate effect. In addition, both vulnerabilities have been added to the Known Exploited Vulnerabilities (KEV) catalog, giving the agencies 24 hours to apply the necessary mitigations.
"CISA is aware of an ongoing exploitation campaign by an advanced threat actor targeting Cisco Adaptive Security Appliances (ASA)," the agency noted.
"The campaign is widespread and involves exploiting zero-day vulnerabilities to gain unauthenticated remote code execution on ASAs, as well as manipulating read-only memory (ROM) to persist through reboot and system upgrade. This activity presents a significant risk to victim networks."
The agency also noted that the activity is linked to a threat cluster dubbed ArcaneDoor, which was previously identified as targeting perimeter network devices from several vendors, including Cisco, to deliver malware families like Line Runner and Line Dancer. The activity was attributed to a threat actor codenamed UAT4356 (aka Storm-1849).
"This threat actor has demonstrated a capability to successfully modify ASA ROM at least as early as 2024," CISA added. "These zero-day vulnerabilities in the Cisco ASA platform are also present in specific versions of Cisco Firepower. Firepower appliances' Secure Boot would detect the identified manipulation of the ROM."
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