CVE-2018-6334 — Multipart-file uploads call variables to be improperly registered in the global

Multipart-file uploads call variables to be improperly registered in the global scope. In cases where variables are not declared explicitly before being used this can lead to unexpected behavior. This affects all supported versions of HHVM prior to the patch (3.25.1, 3.24.5, and

01What is this vulnerability?

Multipart-file uploads call variables to be improperly registered in the global scope. In cases where variables are not declared explicitly before being used this can lead to unexpected behavior. This affects all supported versions of HHVM prior to the patch (3.25.1, 3.24.5, and 3.21.9 and below).

02Affected products

Vendor	Product	Versions
Facebook	HHVM	3.25.2, 3.25.0, 3.24.6, 3.22.0, 3.21.10, unspecified

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2018-12-31T20:00:00.000Z
• Last modified: 2025-05-06T16:48:40.461Z

09References

• github.com — https://github.com/facebook/hhvm/commit/6937de5544c3eead3466b75020d8382080ed0cff
• hhvm.com — https://hhvm.com/blog/2018/03/30/hhvm-3.25.2.html