CVE-1999-1357
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedNetscape 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceNetscape Communicator 4.04-4.7 on UNIX converts the hex characters 0x8b to '<' and 0x9b to '>', allowing remote attackers to inject script via CGI programs that fail to filter these specific characters. This is a client-side cross-site scripting (XSS) vulnerability in the browser itself, where the conversion enables attack payloads that would otherwise be filtered by servers expecting standard angle brackets.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 4.7= 4.04= 4.51CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:L/Au:N/C:P/I:P/A:P
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed browser softwareCheck what web browser is installed on the UNIX system by examining installed packages, application directories, or running 'ls' on common Netscape installation paths such as /usr/local/netscape or ~/.netscapeAffected if The installed browser is anything other than Netscape Communicator for UNIX
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Determine Netscape Communicator versionRun the Netscape browser with version flags such as 'netscape -version' or 'netscape -about', or check the application binary and installation metadata for the exact version numberAffected if The version is not 4.04, 4.51, or any version between 4.05 and 4.7 inclusive
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Confirm operating system is UNIXCheck the operating system using commands like 'uname -a', 'uname -s', or examining /etc/os-release to verify the system is a UNIX variant (Solaris, AIX, HP-UX, Linux, etc.)Affected if The operating system is not a UNIX variant (this vulnerability is specific to UNIX versions of Netscape Communicator)
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Verify the vulnerable character conversion behaviorCreate a test HTML page containing the hex characters 0x8b and 0x9b (encoded as \x8b and \x9b) and open it in the affected Netscape Communicator version to confirm these are rendered as '<' and '>' respectivelyAffected if The browser renders 0x8b as '<' or 0x9b as '>' (this conversion is the core vulnerability mechanism)
A system is affected if it runs Netscape Communicator version 4.04, 4.51, or any version between 4.05 and 4.7 on a UNIX operating system, and the browser exhibits the hex character to angle bracket conversion behavior.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataThis vulnerability affects only obsolete Netscape Communicator 4.x browsers from 1999-2001; modern browsers do not exhibit this character conversion behavior. Organizations should ensure legacy systems are upgraded or decommissioned, and web applications should implement standard input validation regardless.
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- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-1999-1357 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-1999-1357 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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