FortiGate, a popular brand of security appliances designed for network protection, recently discovered a vulnerability in its FortiOS software. As reported in CVE-2019-16151, the improper neutralization of input during web page generation vulnerability (CWE-79) potentially allows remote unauthenticated attackers to exploit it in two malicious ways: redirecting users to harmful websites or executing JavaScript in the victims' browser context. FortiOS versions 6.4.1 and below, along with 6.2.9 and below, are impacted by this vulnerability - specifically when the FortiGate appliance has web filtering and category override configuration enabled.
Redirecting users to malicious websites via a crafted "Host" header
Attackers can manipulate the "Host" header in an HTTP request and craft it in such a way that users can be redirected to a malicious website.
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GET / HTTP/1.1
Executing JavaScript code in the victim's browser context
This exploit involves injecting JavaScript code within the targeted website, leading to potential access and control over sensitive data or even takeover of the victim's web application account.
Exploit Details
The FortiOS vulnerability occurs when the software fails to properly neutralize or filter input during the generation of a web page containing user-controlled data. This often happens when constructing URLs, form inputs, or other user data-dependent components of the web page that an attacker could potentially manipulate.
In the case of CVE-2019-16151, attackers can take advantage of FortiOS' web filtering and category override configurations to exploit the vulnerability. Web filtering is a feature in FortiOS that enables administrators to block, monitor, or allow access to specific categories of websites. The category override feature allows admins to configure FortiGate appliances to override these website categories in specific scenarios or for particular users.
By crafting a malicious "Host" header or injecting JavaScript code in the targeted website, attackers can either redirect users to dangerous websites or execute harmful code in their browser context. The key factor that makes this exploit possible is the attacker's ability to manipulate user data without proper neutralization on the FortiGate appliance.
Original References
1. CVE-2019-16151: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-16151
2. CWE-79: https://cwe.mitre.org/data/definitions/79.html
3. FortiOS 6.4.1: https://docs.fortinet.com/document/fortigate/6.4.1/fortios-release-notes
Mitigation and Recommendations
FortiGate has released updates to address this vulnerability. It is recommended that users update to the latest version of FortiOS to avoid being exploited. Additionally, users should follow best practices in configuring web filtering and category override settings to minimize the chance of exploit. Strong access controls and monitoring of potentially malicious activities can further help protect against such attacks.
Timeline
Published on: 03/21/2025 16:15:13 UTC