How severe is CVE-2021-3420?

CVE-2021-3420 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-2021-3420 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-2021-3420?

CVE-2021-3420 primarily affects Newlib Project Newlib. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-3420?

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-2021-3420 published?

CVE-2021-3420 was published on 2021-03-05 and last updated on 2026-06-17.

CVE-2021-3420

CVE-2021-3420 is a critical-severity vulnerability in Newlib Project Newlib 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: Newlib Project Newlib
Published: 2021-03-05
Last modified: 2026-06-17

Description

A flaw was found in newlib in versions prior to 4.0.0. Improper overflow validation in the memory allocation functions mEMALIGn, pvALLOc, nano_memalign, nano_valloc, nano_pvalloc could case an integer overflow, leading to an allocation of a small buffer and then to a heap-based buffer overflow.

Frequently asked questions

What is CVE-2021-3420?: A flaw was found in newlib in versions prior to 4.0.0. Improper overflow validation in the memory allocation functions mEMALIGn, pvALLOc, nano_memalign, nano_valloc, nano_pvalloc could case an integer overflow, leading to an allocation of a small buffer and then to a heap-based buffer overflow.
How severe is CVE-2021-3420?: CVE-2021-3420 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-2021-3420 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-2021-3420?: CVE-2021-3420 primarily affects Newlib Project Newlib. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-3420?: 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-2021-3420 published?: CVE-2021-3420 was published on 2021-03-05 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:a:newlib_project:newlib:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

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