CVE-2021-24036

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-24. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 3%CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Passing an attacker controlled size when creating an IOBuf could cause integer overflow, leading to an out of bounds write on the heap with the possibility of remote code execution. This issue affects versions of folly prior to v2021.07.22.00. This issue affects HHVM versions prior to 4.80.5, all versions between 4.81.0 and 4.102.1, all versions between 4.103.0 and 4.113.0, and versions 4.114.0, 4.115.0, 4.116.0, 4.117.0, 4.118.0 and 4.118.1.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
50(Track)
EG Risk 50/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation3% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
87.2%
KEV
Not listed

Published

July 23, 2021

Last Modified

November 21, 2024

Advisory Details (3)

Auto-updated May 30, 2026
Patch available. Sources: github_commit.
generic

Facebook

https://www.facebook.com/security/advisories/cve-2021-24036
generic

Security Update | HHVM

https://hhvm.com/blog/2021/07/20/security-update.html
github_commit Patch Available

commit 4f304af1411e (facebook/folly)

Patch available: facebook/folly v2025.10.20.00 (contains commit 4f304af1411e)

https://github.com/facebook/folly/commit/4f304af1411e68851bdd00ef6140e9de4616f7d3

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 48× 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.

Showing the most recent 100 of 103 total refreshes for this CVE.

  1. 2026-07-23 01:58 UTCEG score recompute
  2. 2026-07-22 22:44 UTCEG score recompute
  3. 2026-07-22 14:05 UTCEPSS rescore
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  73. 2026-05-26 13:05 UTCEG score recompute
  74. 2026-05-26 13:05 UTCGHSA enrichment
  75. 2026-05-26 07:17 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-24036?
CVE-2021-24036 is a critical vulnerability published on July 23, 2021. Passing an attacker controlled size when creating an IOBuf could cause integer overflow, leading to an out of bounds write on the heap with the possibility of remote code execution. This issue affects versions of folly prior to v2021.07.22.00. This issue affects HHVM versions prior to 4.80.5, all…
When was CVE-2021-24036 disclosed?
CVE-2021-24036 was first published in the National Vulnerability Database on July 23, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-24036 actively exploited?
CVE-2021-24036 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 87.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-24036?
CVE-2021-24036 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-24036?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-24036, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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