Cisco Secure Firewall ASA/FTD Remote Access SSL VPN Memory Exhaustion DoS
CVE-2026-20103 is a denial-of-service vulnerability in the Remote Access SSL VPN functionality of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software. The flaw is due to trusting user input without validation in the Remote Access SSL VPN service. A remote, unauthenticated attacker can send crafted packets to the Remote Access SSL VPN server and trigger device memory exhaustion. Successful exploitation can cause the device web interface to stop responding and prevent new Remote Access SSL VPN connections from being established. The management interface is not directly affected, although it may become temporarily unresponsive during the condition.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
15 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Unauthenticated remote denial-of-service vulnerability in Cisco ASA and Cisco Secure Firewall Threat Defense (FTD) Remote Access SSL VPN, where crafted packets can exhaust device memory and make the web interface unresponsive, preventing new VPN connections.
Denial of service vulnerability affecting Cisco ASA and Cisco Secure Firewall Threat Defense (FTD) Remote Access SSL VPN.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.