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Vulnerability record · CVE-2020-1900 · published 11 March 2021

CVE-2020-1900: Facebook hhvm use after free vulnerability

Facebook · Hhvm

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.

9.8 CVSS 3.1 Critical EPSS 1.4% · top 28.9% CWE-416 · Use after free
9.8CVSS 3.1 base score, v2 7.5
1.4%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/facebook/hhvm/commit/c1c4bb0cf9e076aafaf4ff3515556ef9faf906f3 PatchThird Party Advisory
https://hhvm.com/blog/2020/06/30/security-update.html Vendor Advisory
https://github.com/facebook/hhvm/commit/c1c4bb0cf9e076aafaf4ff3515556ef9faf906f3 PatchThird Party Advisory
https://hhvm.com/blog/2020/06/30/security-update.html Vendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-1900), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.