Cisco ASA, FTD, IOS products remote code execution
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Multiple critical RCE vulnerabilities in Cisco firewalls and routers; CVE-2025-20333 and CVE-2025-20362 are actively exploited.
Cisco PSIRT has confirmed active exploitation of multiple critical vulnerabilities across Cisco Secure Firewall ASA, Secure Firewall Threat Defense (FTD), and IOS family products. CVE-2025-20362 allows unauthenticated remote attackers to bypass authentication on VPN web server endpoints through improper HTTP input validation. CVE-2025-20333 requires valid VPN credentials but allows authenticated attackers to execute arbitrary code as root through similar input validation flaws. CVE-2025-20363 affects web services across Cisco ASA, FTD, IOS, IOS XE, and IOS XR, enabling unauthenticated RCE on ASA/FTD and authenticated RCE on IOS variants.
Successful exploitation of these flaws could result in complete compromise of affected devices running as root. The vulnerabilities stem from inadequate input validation on HTTP(S) requests to VPN and web service endpoints. Cisco Secure Firewall Management Center (FMC) software is also affected. PSIRT is actively tracking in-the-wild exploitation attempts, particularly for CVE-2025-20333 and CVE-2025-20362, making immediate patching critical for affected networks.
Mentioned in this report
Detection guidance
Suspicious Input in Requests to Cisco ASA/FTD VPN Web Endpoints
Detects HTTP requests to Cisco ASA/FTD WebVPN endpoints that carry path traversal, encoded traversal or shell metacharacters in the URI or query, consistent with input-validation exploitation attempts against the VPN web server. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Suspicious Input in Requests to Cisco ASA/FTD VPN Web Endpoints
status: experimental
description: Detects HTTP requests to Cisco ASA/FTD WebVPN endpoints that carry path
traversal, encoded traversal or shell metacharacters in the URI or query, consistent
with input-validation exploitation attempts (authentication bypass or RCE) against
the VPN web server. Requires web or reverse-proxy logs that cover traffic to the
VPN portal. Generalises on the malformed-input pattern, not on a specific payload.
tags:
- attack.initial-access
- attack.t1190
logsource:
category: webserver
detection:
selection_endpoint:
cs-uri-stem|contains:
- /+CSCOE+/
- /+CSCOU+/
- /+webvpn+/
selection_malformed_stem:
cs-uri-stem|contains:
- ../
- ..%2f
- '%2e%2e%2f'
- '%252e%252e'
- '%00'
selection_malformed_query:
cs-uri-query|contains:
- ../
- ..%2f
- '%2e%2e%2f'
- '%00'
- $(
- '`'
- '%24%28'
- '|sh'
- ;sh
- /bin/sh
- /bin/bash
condition: selection_endpoint and 1 of selection_malformed_*
falsepositives:
- Vulnerability scanners run by the organisation against the VPN portal
- Unusual but benign portal bookmarks or URLs containing encoded characters
level: medium
id: 26a1fde6-e410-59fb-a70b-ce15e96daf59
author: Vorant
references:
- https://www.cisecurity.org/advisory/multiple-vulnerabilities-in-cisco-products-could-allow-for-remote-code-execution_2025-091
Behavioural rules are generated from public reporting — validate in your environment before deploying.
Source reporting: https://www.cisecurity.org/advisory/multiple-vulnerabilities-in-cisco-products-could-allow-for-remote-code-execution_2025-091
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