How severe is CVE-2021-24036?

CVE-2021-24036 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-24036 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-24036?

CVE-2021-24036 primarily affects Facebook Folly. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-24036?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-24036 published?

CVE-2021-24036 was published on 2021-07-23 and last updated on 2026-06-17.

CVE-2021-24036

CVE-2021-24036 is a critical-severity vulnerability in Facebook Folly with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-190.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (87th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-190
Affected product: Facebook Folly
Published: 2021-07-23
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-24036?: 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.
How severe is CVE-2021-24036?: CVE-2021-24036 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-24036 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-24036?: CVE-2021-24036 primarily affects Facebook Folly. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-24036?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-24036 published?: CVE-2021-24036 was published on 2021-07-23 and last updated on 2026-06-17.

References

Affected products (8)

cpe:2.3:a:facebook:folly:*:*:*:*:*:*:*:*
cpe:2.3:a:facebook:hhvm:*:*:*:*:*:*:*:*
cpe:2.3:a:facebook:hhvm:4.114.0:*:*:*:*:*:*:*
cpe:2.3:a:facebook:hhvm:4.115.0:*:*:*:*:*:*:*
cpe:2.3:a:facebook:hhvm:4.116.0:*:*:*:*:*:*:*
cpe:2.3:a:facebook:hhvm:4.117.0:*:*:*:*:*:*:*
cpe:2.3:a:facebook:hhvm:4.118.0:*:*:*:*:*:*:*
cpe:2.3:a:facebook:hhvm:4.118.1:*:*:*:*:*:*:*

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