Is CVE-2021-28831 in the CISA KEV catalog?

No. CVE-2021-28831 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-28831?

CVE-2021-28831 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2021-28831?

CVE-2021-28831 has an EPSS score of 2.72% (84th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-28831?

Upgrade busybox on debian 11 to 1:1.30.1-6+deb11u1 or later. Fixes are available for 4 affected products.

CVE & CISA-KEV Catalog

CVE-2021-28831

HIGHEPSS 84th pctl

7.5

CVSS v3

NVD

Description

decompress_gunzip.c in BusyBox through 1.32.1 mishandles the error bit on the huft_build result pointer, with a resultant invalid free or segmentation fault, via malformed gzip data.

CWE-755

How to fix

Remediation Available

busyboxDebian

Fixed in:1:1.30.1-6+deb11u1CVE-2021-28831

Fixed in:1:1.35.0-1CVE-2021-28831

busyboxUbuntu

Fixed in:1:1.21.0-1ubuntu1.4+esm1USN-6335-1

Fixed in:1:1.22.0-15ubuntu1.4+esm1USN-5179-2

Fixed in:1:1.22.0-15ubuntu1.4+esm2USN-6335-1

Fixed in:1:1.27.2-2ubuntu3.4+esm1USN-6335-1

Fixed in:1:1.27.2-2ubuntu3.4USN-5179-1

Fixed in:1:1.30.1-4ubuntu6.4USN-5179-1

busybox-initramfsUbuntu

Fixed in:1:1.21.0-1ubuntu1.4+esm1USN-6335-1

Fixed in:1:1.22.0-15ubuntu1.4+esm2USN-6335-1

Fixed in:1:1.22.0-15ubuntu1.4+esm1USN-5179-2

Fixed in:1:1.27.2-2ubuntu3.4+esm1USN-6335-1

Fixed in:1:1.27.2-2ubuntu3.4USN-5179-1

Fixed in:1:1.30.1-4ubuntu6.4USN-5179-1

busybox-staticUbuntu

Fixed in:1:1.21.0-1ubuntu1.4+esm1USN-6335-1

Fixed in:1:1.22.0-15ubuntu1.4+esm1USN-5179-2

Fixed in:1:1.22.0-15ubuntu1.4+esm2USN-6335-1

Fixed in:1:1.27.2-2ubuntu3.4+esm1USN-6335-1

Fixed in:1:1.27.2-2ubuntu3.4USN-5179-1

Fixed in:1:1.30.1-4ubuntu6.4USN-5179-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploit Intelligence

2.72%probability of exploitation in 30 days

84thpercentile

Elevated risk: more likely to be exploited than 84% of all known CVEs.

References

Patch1

git.busybox.net

Third-Party Advisory2

Other references5

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-12-17.