Medium

Authentication bypass and portal modification in Cisco ASA Clientless SSL VPN

IdentifiersCVE-2014-3393CWE-287· Improper Authentication

CVE-2014-3393 is an improper-authentication vulnerability in the Cisco ASA Clientless SSL VPN portal customization framework. An unauthenticated remote attacker can modify customization objects in the RAMFS cache and alter portal content, including injecting malicious JavaScript for cross-site scripting and credential theft. Affected releases are 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 vulnerability is tracked as Cisco bug CSCup36829.

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ANALYST BRIEF

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.

Attackers can tamper with the VPN portal before authentication and implant JavaScript that captures credentials, keystrokes, cookies, or session information when users interact with the modified portal. Observed exploitation involved malicious JavaScript added to SSL VPN landing pages. Stolen session information can enable session reuse and traffic replay even when two-factor authentication is required. The authentication bypass permits portal modification; it does not by itself establish unrestricted access to internal VPN resources.

Mitigation

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

Inspect Clientless SSL VPN portal customizations for unauthorized changes and malicious JavaScript. Restrict ASDM access using ACLs and avoid Internet exposure to reduce the separate risk of portal modification through compromised administrative access. Two-factor authentication is not a complete mitigation: injected JavaScript can steal session cookies or hijack and reuse authentication tokens.

Remediation

Patch, then assume compromise.

Upgrade affected Cisco ASA releases to at least the corresponding fixed version: 8.2(5.51), 8.3(2.42), 8.4(7.23), 8.6(1.14), 9.0(4.24), 9.1(5.12), or 9.2(2.4).

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

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.

VendorProductType

Cisco SystemsAdaptive Security Appliance Softwareoperating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

4 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

4 SOURCESView more in app

fireeyeNews

Feb 3, 2026

A pre-authentication cross-site scripting vulnerability in Cisco ASA VPN (SSL VPN portal) that can be exploited to inject malicious JavaScript into the VPN login/landing page, enabling credential/session theft and subsequent unauthorized VPN access.

fireeyeNews

Feb 3, 2026

A pre-authentication cross-site scripting vulnerability in Cisco ASA SSL VPN (VPN concentrator) that can be exploited to inject malicious JavaScript into the VPN portal and steal user credentials/session information (enabling subsequent unauthorized VPN access and potential replay).

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware2

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

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Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity