CVE-2020-1900

9.8 criticalEPSS 1.4%

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.

Severity

CVSS 3.1

9.8 critical

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

EPSS: 1.4% chance of exploitation in the next 30 days; higher than 72% of CVEs (scores of 2026-10-31)
CWE: CWE-416
Published: 2021-03-11
Modified: 2026-06-17
Record from: the NVD, synced 2026-10-19

Affected

facebook:hhvm

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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