Heap-Based Buffer Overflow RCE in Cisco ASA/FTD/IOS Web Services
CVE-2025-20363 is a heap-based buffer overflow in the web services components of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Secure Firewall Threat Defense (FTD) Software, Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software. The flaw is caused by improper validation of user-supplied input in HTTP requests. Cisco states that crafted HTTP requests can trigger insufficient heap buffer allocation followed by an out-of-bounds write of attacker-controlled data, resulting in heap memory corruption. On ASA and FTD, exploitation is possible by an unauthenticated remote attacker; on IOS, IOS XE, and IOS XR, exploitation requires an authenticated remote attacker with low privileges. Cisco also notes exploitation may require obtaining additional information about the target system, overcoming exploit mitigations, or both. Successful exploitation can result in arbitrary code execution as root and full compromise of the affected device.
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Impact, mitigation & remediation
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Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
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Remediation
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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
63 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A heap-based buffer overflow vulnerability in Cisco ASA/FTD, potentially allowing unauthenticated remote code execution as root. No evidence of exploitation in the wild as of reporting.
A remote code execution vulnerability in Cisco ASA/FTD (unauthenticated) and some Cisco IOS components (authenticated), allowing arbitrary code execution.
A vulnerability affecting Cisco ASA, FTD, IOS, IOS XE, and IOS XR with Remote Access VPN enabled, allowing arbitrary code execution (unauthenticated on ASA/FTD, authenticated on other platforms).
A Cisco vulnerability listed as trending and critical, but no specific details provided in the content.
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.