What’s Vulnerable › Vulnerabilities

CVE-2020-1900

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-03-11 · updated 2026-06-17
• Weakness: CWE-416

Description

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.

Affected products

• Facebook HHVM: before 4.32.3; from 4.33.0 before 4.56.1; 4.57.0, 4.58.0, 4.58.1, 4.59.0, 4.60.0, 4.61.0 (+1) — fixed in 4.32.3, 4.56.1

How to fix

Upgrade to a fixed version: Facebook HHVM 4.32.3, 4.56.1. Check the vendor advisory for mitigations.

References

• https://github.com/facebook/hhvm/commit/c1c4bb0cf9e076aafaf4ff3515556ef9faf906f3
• https://hhvm.com/blog/2020/06/30/security-update.html
• https://github.com/facebook/hhvm/commit/c1c4bb0cf9e076aafaf4ff3515556ef9faf906f3
• https://hhvm.com/blog/2020/06/30/security-update.html

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