CVE-2020-1900

When unserializing an object with dynamic properties HHVM needs to pre-reserve the full size of the dynamic property array before inserting anything into it. Otherwise the array might resize, invalidating previously stored references. This pre-reservation was not occurring in 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-2020-1900 is rated Moderate Risk (63.8/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 1.38%). 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-2020-1900

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 0.81% 1.38% +0.58%
2 2025-12-28 0.66% 0.81% +0.15%
3 2025-12-27 — 0.66% —

Full EPSS history (15 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-1900

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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: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: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.
 3.9 5.9 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/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:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2020-1900

OS Trackers for CVE-2020-1900

vendor priority summary link
ubuntu low CVE-2020-1900 low 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-2020-1900

Affected software / configurations for CVE-2020-1900

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-2020-1900

cvelogic Threat Intelligence