Netscape Communicator GIF Comment JavaScript Execution
Severe, but no confirmed exploitation yet. Schedule remediation in your next patch cycle and apply mitigations if you're exposed.
An unauthenticated attacker, remotely over the network, can cause limited impact to confidentiality and integrity and availability.
Netscape Communicator before 4.77 allows remote attackers to execute arbitrary Javascript via a GIF image whose comment contains the Javascript.
Inferred from the weakness type (CWE) and how the flaw is reached — the techniques an attacker would chain to exploit this. Real-world corroboration appears here as threat intel is folded in.
Generated by Wavense from the CVE record — an immediate mitigation and the permanent fix.
To reduce immediate risk, users should avoid opening or viewing GIF images from untrusted sources while using affected browser versions. Organizations can implement email and web proxy filters to block or sanitize untrusted GIF files, especially those with unusual comment metadata. Consider using an alternative, more secure browser for critical tasks until the primary browser can be updated.
The permanent resolution is to upgrade Netscape Communicator to version 4.77 or a later, patched version. This update addresses the vulnerability by correctly sanitizing or preventing JavaScript execution from GIF comments. All installations of Netscape Communicator prior to 4.77 are affected and should be updated promptly to mitigate this remote code execution risk.
An attacker can embed arbitrary JavaScript within the comment section of a GIF image. When a user views this crafted GIF in Netscape Communicator prior to version 4.77, the embedded script executes within their browser context. This allows for session hijacking, data exfiltration from viewed websites, or defacement of the user's browser session, leading to significant privacy and security risks.
No CWE classification has been assigned.
Other CVEs affecting communicator
Buffer overflow in the HTML parser for Netscape 4.75 and earlier allows remote attackers to execute arbitrary commands via a long password value in a form field.
Netscape Communicator does not properly prevent a ServerSocket object from being created by untrusted entities, which allows remote attackers to create a server on the victim's system via a malicious applet, as demonstrated by Brown Orifice.
Buffer overflow in Netscape Navigator/Communicator 4.7 for Windows 95 and Windows 98 allows remote attackers to cause a denial of service, and possibly execute arbitrary commands, via a long argument after the ? character in a URL that references an .asp, .cgi, .html, or .pl file.
Netscape Communicator 4.04 through 4.7 (and possibly other versions) in various UNIX operating systems converts the 0x8b character to a "<" sign, and the 0x9b character to a ">" sign, which could allow remote attackers to attack other clients via cross-site scripting (CSS) in CGI programs that do not filter these characters.
The byte code verifier component of the Java Virtual Machine (JVM) allows remote execution through malicious web pages.
A configuration in a web browser such as Internet Explorer or Netscape Navigator allows execution of active content such as ActiveX, Java, Javascript, etc.