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Authentication Bypass in Cisco ASA Clientless SSL VPN Portal Customization Framework

IdentifiersCVE-2014-3393CWE-287· Improper Authentication

CVE-2014-3393 affects the Clientless SSL VPN portal customization framework in Cisco ASA Software 8.2 before 8.2(5.51), 8.3 before 8.3(2.42), 8.4 before 8.4(7.23), 8.6 before 8.6(1.14), 9.0 before 9.0(4.24), 9.1 before 9.1(5.12), and 9.2 before 9.2(2.4). The flaw is caused by improper implementation of authentication in the portal customization framework, allowing a remote unauthenticated attacker to modify Clientless SSL VPN portal customization objects stored in the RAMFS cache filesystem. In practice, this enables alteration of portal content such as the WebVPN login page, including insertion of malicious JavaScript/XSS payloads. Public reporting and incident-response observations show the vulnerability was exploited to inject credential-stealing scripts into Cisco ASA SSL VPN landing pages.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

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Successful exploitation allows an unauthenticated remote attacker to tamper with the Clientless SSL VPN portal presented to users. Observed abuse included injecting malicious JavaScript into logon pages to capture usernames, passwords, keystrokes, cookies, and session information. This can lead to credential theft, session hijacking, and unauthorized access to internal resources exposed through the VPN portal. Reporting also indicates that two-factor authentication does not fully prevent abuse because stolen session cookies or replayable session information may still permit attacker access.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure by disabling Clientless SSL VPN/WebVPN customization where feasible, closely monitoring portal content for unauthorized changes, and restricting management access such as ASDM with ACLs and by removing Internet exposure. Because exploitation has been used for credential and session theft, enable MFA but do not rely on it as a complete mitigation; additionally force reauthentication, expire sessions, rotate credentials, and review logs for anomalous VPN access. Threat hunting should include inspection of ASA portal files, RAMFS customization objects, and externally loaded JavaScript references.

Remediation

Patch, then assume compromise.

Upgrade Cisco ASA Software to a fixed release. The affected trains are fixed in 8.2(5.51), 8.3(2.42), 8.4(7.23), 8.6(1.14), 9.0(4.24), 9.1(5.12), and 9.2(2.4) or later, as applicable. Organizations should also inspect Clientless SSL VPN portal customization objects and login pages for unauthorized modifications, remove any injected scripts, rotate potentially exposed user credentials, invalidate active VPN sessions, and review administrative access and device integrity for signs of follow-on compromise.
PUBLIC EXPLOITS

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VALID 0 / 0 TOTALView more in app

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EXPOSURE SURFACE

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VendorProductType
Cisco SystemsAdaptive Security Appliance Softwareoperating_system

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Threat actor evidence1

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Associated malware2

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