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.
CVE-2020-1898
This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.8%, top 25% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(medium)
- EPSS
- 64.8%
- KEV
- Not listed
Published
March 11, 2021
Last Modified
November 21, 2024
References (4)
- cve-assign@fbhttps://github.com/facebook/hhvm/commit/1746dfb11fc0048366f34669e74318b8278a684c
- cve-assign@fbhttps://hhvm.com/blog/2020/06/30/security-update.html
- af854a3a-2127-422b-91ae-364da2661108https://github.com/facebook/hhvm/commit/1746dfb11fc0048366f34669e74318b8278a684c
- af854a3a-2127-422b-91ae-364da2661108https://hhvm.com/blog/2020/06/30/security-update.html
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 11× in last 7d / 44× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-11 08:25 UTCEPSS rescore
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- 2026-07-09 19:07 UTCEPSS rescore
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- 2026-07-01 15:03 UTCEPSS rescore
- 2026-07-01 07:18 UTCOSV refresh
- 2026-06-30 23:20 UTCEPSS rescore
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- 2026-06-23 21:31 UTCEPSS rescore
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- 2026-06-13 12:13 UTCOSV refresh
- 2026-06-12 23:10 UTCEPSS rescore
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- 2026-05-29 13:42 UTCEPSS rescore
- 2026-05-28 13:43 UTCEPSS rescore
- 2026-05-28 13:43 UTCEPSS rescore
- 2026-05-27 13:39 UTCEPSS rescore
- 2026-05-26 19:55 UTCEG score recompute
- 2026-05-26 19:55 UTCGHSA enrichment
- 2026-05-26 13:42 UTCEPSS rescore
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- 2026-05-26 07:17 UTCEPSS rescore
- 2026-05-26 07:17 UTCEPSS rescore
- 2026-05-24 16:48 UTCEPSS rescore
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Frequently asked(5)
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Dependency Blast Radius
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