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Fencer Vulns
high 7.5

CVE-2021-28831 json

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 s…

published 2021-03-19 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-15487

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.7%
EPSS 2.7% chance of exploitation in 30 days, percentile 86%
public exploits
0
none known

Summary

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.

Patch / fix

  • busybox Debian 14, Debian 13, Debian 12 1:1.35.0-1

debian advisories DEBIAN-CVE-2021-28831

  • busybox Ubuntu 18.04 LTS 1:1.27.2-2ubuntu3.4
  • busybox Ubuntu 20.04 LTS 1:1.30.1-4ubuntu6.4
  • busybox Ubuntu 22.04 LTS 1:1.30.1-7ubuntu2
  • busybox Ubuntu Pro 14.04 LTS 1:1.21.0-1ubuntu1.4+esm1
  • busybox Ubuntu Pro 16.04 LTS 1:1.22.0-15ubuntu1.4+esm1

ubuntu advisories UBUNTU-CVE-2021-28831

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • busybox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES 12 SP5 +5 more 1.35.0-4.3.1
  • busybox SLE Module for Basesystem 15 SP4, openSUSE Leap 15.4 1.35.0-150400.3.3.1
  • busybox SLES 15 SP2-BCL, SLES 15 SP1-BCL, SLE Real Time 15 SP2 +18 more 1.34.1-4.9.1
  • busybox SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +9 more 1.26.2-4.5.1

suse advisories SUSE-SU-2022:4253-1SUSE-SU-2022:3959-1SUSE-SU-2022:0135-2SUSE-SU-2022:0135-1SUSE-SU-2021:3531-1

  • busybox openSUSE Tumbleweed 1.35.0-1.1
  • busybox openSUSE Leap 15.3 1.34.1-4.9.1
  • virtualbox openSUSE Leap 15.3 6.1.34-lp153.2.27.2
  • virtualbox-kmp openSUSE Leap 15.3 6.1.34-lp153.2.27.1
  • busybox openSUSE Leap 15.2 1.26.2-lp152.5.3.1
  • busybox openSUSE Leap 15.3 1.26.2-4.5.1

opensuse advisories openSUSE-SU-2024:11738-1openSUSE-SU-2022:0135-1openSUSE-SU-2021:1408-1openSUSE-SU-2021:3531-1

  • busybox Alpine 3.10 1.30.1-r5
  • busybox Alpine 3.11 1.31.1-r10
  • busybox Alpine 3.12 1.31.1-r20
  • busybox Alpine 3.13 1.32.1-r4
  • busybox Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 1.33.0-r5

alpine advisories ALPINE-CVE-2021-28831

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • busybox CBL-Mariner 2.0 1.32.0-2

azure linux advisories AZL-6342

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • busybox Arch Linux 1.32.1-4
  • mkinitcpio-busybox Arch Linux 1.32.1-3

arch linux advisories AVG-1707AVG-1708

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-28831 updated cvss 7.5

busybox: invalid free or segmentation fault via malformed gzip data

  • Red Hat Enterprise Linux 6 busybox, busybox-petitboot
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-23-166-10 updated cvss 7.5

Siemens SIMATIC S7-1500 TM MFP BIOS

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
10 mo ago

Exploit prediction

2.72% chance of exploitation in the next 30 days, higher than 86% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AC:L/AV:N/A:H/C:N/I:N/PR:N/S:U/UI:N
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness
  • CWE-755 Improper Handling of Exceptional Conditions

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.