A potential denial-of-service issue in the Proxygen handling of invalid HTTP2 settings which can cause the server to spend disproportionate…

published 2018-12-03 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-18093

cvss: 5.9; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.1%; EPSS 1.1% chance of exploitation in 30 days, percentile 65%
public exploits: 0; none known

A potential denial-of-service issue in the Proxygen handling of invalid HTTP2 settings which can cause the server to spend disproportionate resources. This affects all supported versions of HHVM (3.24.3 and 3.21.7 and below) when using the proxygen server to handle HTTP2 requests.

Patch / fix

fixed in 1

Facebook HHVM 3.21.8

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 18 mo ago (2025-05-06)

Exploit prediction

1.09% chance of exploitation in the next 30 days, higher than 65% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	3.0	5.9	CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:N/I:N/A:P

Affected products

Facebook HHVM

Classification

Weakness

CWE-400 Uncontrolled Resource Consumption
CWE-19 Data Processing Errors

References

hhvm.com /blog/2018/03/15/hhvm-3.25.html
vendor-advisory

Sources

CVE List CVE-2018-6332
NVD CVE-2018-6332

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary