How severe is CVE-2021-31870?

CVE-2021-31870 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-2021-31870 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-31870?

CVE-2021-31870 primarily affects Klibc Project Klibc. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-31870?

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-2021-31870 published?

CVE-2021-31870 was published on 2021-04-30 and last updated on 2026-06-17.

CVE-2021-31870

CVE-2021-31870 is a critical-severity vulnerability in Klibc Project Klibc 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: 2% (79th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-190
Affected product: Klibc Project Klibc
Published: 2021-04-30
Last modified: 2026-06-17

Description

An issue was discovered in klibc before 2.0.9. Multiplication in the calloc() function may result in an integer overflow and a subsequent heap buffer overflow.

Frequently asked questions

What is CVE-2021-31870?: An issue was discovered in klibc before 2.0.9. Multiplication in the calloc() function may result in an integer overflow and a subsequent heap buffer overflow.
How severe is CVE-2021-31870?: CVE-2021-31870 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-2021-31870 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-31870?: CVE-2021-31870 primarily affects Klibc Project Klibc. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-31870?: 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-2021-31870 published?: CVE-2021-31870 was published on 2021-04-30 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:klibc_project:klibc:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

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