What’s Vulnerable › Vulnerabilities

CVE-2020-1898

• 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-674

Description

The fb_unserialize function did not impose a depth limit for nested deserialization. That meant a maliciously constructed string could cause deserialization to recurse, leading to stack exhaustion. 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/1746dfb11fc0048366f34669e74318b8278a684c
• https://hhvm.com/blog/2020/06/30/security-update.html
• https://github.com/facebook/hhvm/commit/1746dfb11fc0048366f34669e74318b8278a684c
• https://hhvm.com/blog/2020/06/30/security-update.html

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