What’s Vulnerable › Vulnerabilities

CVE-2020-1899

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.2% 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-822

Description

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.

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/1107228a5128d3ca1c4add8ac1635d933cbbe2e9
• https://hhvm.com/blog/2020/06/30/security-update.html
• https://github.com/facebook/hhvm/commit/1107228a5128d3ca1c4add8ac1635d933cbbe2e9
• https://hhvm.com/blog/2020/06/30/security-update.html

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