CVE-2020-1899

The unserialize() function supported a type code, "S", which was meant to be supported only for APC serialization. This type code allowed arbitrary memory addresses to be accessed as if they were static StringData objects. This issue affected HHVM prior to v4.32.3, between versions 4.33.0 and 4.56.0, 4.57.0, 4.58.0, 4.58.1, 4.59.0, 4.60.0, 4.61.0, 4.62.0.

Published: 2021-03-10 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-1899 is rated Moderate Risk (53.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.22%). 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-2020-1899

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 2026-06-15 0.36% 1.22% +0.86%
2 2025-12-28 0.32% 0.36% +0.04%
3 2025-12-27 — 0.32% —

Full EPSS history (14 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-1899

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N 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:N)
No account or special rights needed—anonymous or random user is enough.
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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:N/A:N 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:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2020-1899

OS Trackers for CVE-2020-1899

vendor priority summary link
ubuntu medium CVE-2020-1899 medium priority: Ubuntu including 1 source packages (hhvm), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 13, needs-triage 3. https://ubuntu.com/security/CVE-2020-1899

Affected software / configurations for CVE-2020-1899

Vendor Product Version Raw CPE
facebook hhvm < 4.32.3 cpe:2.3:a:facebook:hhvm:*:*:*:*:*:*:*:*
facebook hhvm >= 4.33.0, < 4.56.1 cpe:2.3:a:facebook:hhvm:*:*:*:*:*:*:*:*
facebook hhvm 4.57.0 cpe:2.3:a:facebook:hhvm:4.57.0:*:*:*:*:*:*:*
facebook hhvm 4.58.0 cpe:2.3:a:facebook:hhvm:4.58.0:*:*:*:*:*:*:*
facebook hhvm 4.58.1 cpe:2.3:a:facebook:hhvm:4.58.1:*:*:*:*:*:*:*
facebook hhvm 4.59.0 cpe:2.3:a:facebook:hhvm:4.59.0:*:*:*:*:*:*:*
facebook hhvm 4.60.0 cpe:2.3:a:facebook:hhvm:4.60.0:*:*:*:*:*:*:*
facebook hhvm 4.61.0 cpe:2.3:a:facebook:hhvm:4.61.0:*:*:*:*:*:*:*
facebook hhvm 4.62.0 cpe:2.3:a:facebook:hhvm:4.62.0:*:*:*:*:*:*:*

References for CVE-2020-1899

cvelogic Threat Intelligence