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Vulnerabilities/CVE-1999-0440
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CVE-1999-0440

Java Virtual Machine Byte Code Verifier Remote Execution

VendornetscapePublishedMar 1, 1999SourceNVD
Plan a fix

Severe, but no confirmed exploitation yet. Schedule remediation in your next patch cycle and apply mitigations if you're exposed.

Severity
High · 7.5
CVSS base score
Exploitation
Not observed
No known exploitation or public exploit
Exploit likelihood
4%
Chance of exploitation in 30 days (EPSS)
Exposure
Remote
Exploitable over the network without credentials
01

What's the risk?

An unauthenticated attacker, remotely over the network, can cause limited impact to confidentiality and integrity and availability.

The byte code verifier component of the Java Virtual Machine (JVM) allows remote execution through malicious web pages.

How it's exploitedMITRE ATT&CK · inferred from weakness & vector
Initial Access
T1190Exploit Public-Facing Application

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.

02

Are we affected?

13
  • Affectednetscape · communicator4.5
  • Affectednetscape · navigator4.0
  • Affectednetscape · navigator4.01
  • Affectednetscape · navigator4.02
  • Affectednetscape · navigator4.03
  • Affectednetscape · navigator4.04
  • Affectednetscape · navigator4.05
  • Affectednetscape · navigator4.5
  • Affectednetscape · navigator4.06
  • Affectednetscape · navigator4.07
  • Affectednetscape · navigator4.08
  • Affectednetscape · navigator4.61
  • Affectedsun · javaall versions
03

What to do

Generated by Wavense from the CVE record — an immediate mitigation and the permanent fix.

  1. !

    Mitigate now

    Temporarily disable Java applet execution in web browsers or configure strict security settings to block untrusted applets. Implement network egress filtering to prevent unexpected outbound connections from client machines, and enhance endpoint detection and response (EDR) monitoring for suspicious process execution originating from browser activity.

  2. ✓

    Permanent fix

    Apply the latest security patches or upgrade the Java Virtual Machine (JVM) to a version that includes fixes for the byte code verifier vulnerability. Consult vendor advisories for specific update instructions and ensure all client systems running Java are updated to a secure version to prevent exploitation.

Technical details— weakness, CVSS vector & calculator, related CVEs

Business impact

An attacker can embed malicious Java applets into web pages, exploiting the JVM's byte code verifier to execute arbitrary code on a victim's machine. This allows for full system compromise, leading to data exfiltration, installation of malware, or disruption of critical services, posing significant risks to sensitive information and operational integrity.

Weakness

No CWE classification has been assigned.

CVSS 2.0 details

AV:N/AC:L/Au:N/C:P/I:P/A:P
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Confidentiality
Low
Integrity
Low
Availability
Low

Related vulnerabilities

Other CVEs affecting communicator

NVD
10.0Critical
CVE-2021-44228KEV⚙ WeaponizedExploit likely

Apache Log4j2 2.0-beta9 through 2.15.0 (excluding security releases 2.12.2, 2.12.3, and 2.3.1) JNDI features used in configuration, log messages, and parameters do not protect against attacker controlled LDAP and other JNDI related endpoints. An attacker who can control log messages or log message parameters can execute arbitrary code loaded from LDAP servers when message lookup substitution is enabled. From log4j 2.15.0, this behavior has been disabled by default. From version 2.16.0 (along with 2.12.2, 2.12.3, and 2.3.1), this functionality has been completely removed. Note that this vulnerability is specific to log4j-core and does not affect log4net, log4cxx, or other Apache Logging Services projects.

ciscoCWE-20Improper Input ValidationNetworkLow effortNo authNo interactionCIA
2021-12-10
NVD
9.0Critical
CVE-2021-45046KEV⚙ WeaponizedExploit likely

It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allows attackers with control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout with either a Context Lookup (for example, $${ctx:loginId}) or a Thread Context Map pattern (%X, %mdc, or %MDC) to craft malicious input data using a JNDI Lookup pattern resulting in an information leak and remote code execution in some environments and local code execution in all environments. Log4j 2.16.0 (Java 8) and 2.12.2 (Java 7) fix this issue by removing support for message lookup patterns and disabling JNDI functionality by default.

siemensCWE-917Expression Language InjectionNetworkHigh effortNo authNo interactionCIA
2021-12-14
NVD
7.5High
CVE-2001-0596PoC

Netscape Communicator before 4.77 allows remote attackers to execute arbitrary Javascript via a GIF image whose comment contains the Javascript.

netscapeNetworkLow effortNo authCIA
2001-08-02
NVD
7.5High
CVE-2000-1187

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.

netscapeNetworkLow effortNo authCIA
2001-01-09
NVD
7.5High
CVE-2000-0711PoC

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.

netscapeNetworkLow effortNo authCIA
2000-10-20
NVD
7.5High
CVE-1999-1189

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.

netscapeNetworkLow effortNo authCIA
1999-11-24
NVD
7.5High
CVE-1999-1357

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.

netscapeNetworkLow effortNo authCIA
1999-10-05
NVD
7.5High
CVE-1999-0537

A configuration in a web browser such as Internet Explorer or Netscape Navigator allows execution of active content such as ActiveX, Java, Javascript, etc.

microsoftNetworkLow effortNo authCIA
1998-03-31
0.0
/ 10.0 base
High severity
Key facts
CVE ID
CVE-1999-0440
Published
Mar 1, 1999
Last modified
Jun 16, 2026
CVSS
7.5 (v2.0)
EPSS
3.64%
In CISA KEV
No
Confidence
86/100
Timeline
  1. Mar 1, 1999Published to NVDNVD
  2. Jun 16, 2026Record last modifiedNVD
  3. Aug 22, 2026AI analysis generatedWavense
View on NVD