CVE-2018-6337 Weak cryptography in HHVM

High 7.5 Published 31 Dec 2018 Updated 6 May 2025

Forked processes reuse random buffers, causing predictable random numbers and weakening cryptographic security in applications using the folly library.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2018-6337?

CVE-2018-6337 is a high-severity vulnerability in Facebook HHVM, published on 31 Dec 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

folly::secureRandom will re-use a buffer between parent and child processes when fork() is called. That will result in multiple forked children producing repeat (or similar) results. This affects HHVM 3.26 prior to 3.26.3 and the folly library between v2017.12.11.00 and v2018.08.09.00.

Weakness: CWE-119, CWE-212

Which versions are affected by CVE-2018-6337?

It affects 2 products.

Products include Facebook Folly, Facebook Hhvm.

How do I fix CVE-2018-6337?

No fix has been published for CVE-2018-6337 yet. Limit exposure of the affected software until one is available.

Is CVE-2018-6337 being exploited?

There is no known exploitation of CVE-2018-6337 in the wild and no public exploit code.

Sources

Also known as GHSA-46jm-3g2r-j53x.