CVE-2019-3556

HHVM supports the use of an "admin" server which accepts administrative requests over HTTP. One of those request handlers, dump-pcre-cache, can be used to output cached regular expressions from the current execution context into a file. The handler takes a parameter which specifies where on the filesystem to write this data. The parameter is not validated, allowing a malicious user to overwrite arbitrary files where the user running HHVM has write access. This issue affects HHVM versions prior to 4.56.2, all versions between 4.57.0 and 4.78.0, as well as 4.79.0, 4.80.0, 4.81.0, 4.82.0, and 4.83.0.

Published: 2021-10-26 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2019-3556 is rated Moderate Risk (61.3/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.67%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2019-3556

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-12-28 1.29% 1.67% +0.37%
2 2025-12-27 1.67% 1.29% -0.37%
3 2025-10-28 — 1.67% —

Full EPSS history (13 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2019-3556

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.1 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.2 [email protected]
5.5 2.0 MEDIUM
AV:N/AC:L/Au:S/C:N/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 4.9 [email protected]

Weakness enumeration for CVE-2019-3556

OS Trackers for CVE-2019-3556

vendor priority summary link
ubuntu medium CVE-2019-3556 medium priority: Ubuntu including 1 source packages (hhvm), 4 status rows across 4 suites (bionic, trusty, upstream, xenial): needs-triage 3, ignored 1. https://ubuntu.com/security/CVE-2019-3556

Affected software / configurations for CVE-2019-3556

Vendor Product Version Raw CPE
facebook hhvm < 4.56.2 cpe:2.3:a:facebook:hhvm:*:*:*:*:*:*:*:*
facebook hhvm >= 4.57.0, <= 4.78.0 cpe:2.3:a:facebook:hhvm:*:*:*:*:*:*:*:*
facebook hhvm 4.79.0 cpe:2.3:a:facebook:hhvm:4.79.0:*:*:*:*:*:*:*
facebook hhvm 4.80.0 cpe:2.3:a:facebook:hhvm:4.80.0:*:*:*:*:*:*:*
facebook hhvm 4.81.0 cpe:2.3:a:facebook:hhvm:4.81.0:*:*:*:*:*:*:*
facebook hhvm 4.82.0 cpe:2.3:a:facebook:hhvm:4.82.0:*:*:*:*:*:*:*
facebook hhvm 4.83.0 cpe:2.3:a:facebook:hhvm:4.83.0:*:*:*:*:*:*:*

References for CVE-2019-3556

cvelogic Threat Intelligence