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Fencer Vulns
medium 5.5

CVE-2021-42375 json

An incorrect handling of a special element in Busybox's ash applet leads to denial of service when processing a crafted shell command, due…

published 2021-11-15 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-29346

cvss
5.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

An incorrect handling of a special element in Busybox's ash applet leads to denial of service when processing a crafted shell command, due to the shell mistaking specific characters for reserved characters. This may be used for DoS under rare conditions of filtered command input.

Patch / fix

  • busybox busybox 1.34.0
  • busybox Debian 14, Debian 13, Debian 12 1:1.35.0-1

debian advisories DEBIAN-CVE-2021-42375

  • 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

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

  • 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

opensuse advisories openSUSE-SU-2022:0135-1

  • busybox Alpine 3.13 1.32.1-r7
  • busybox Alpine 3.14 1.33.1-r5
  • busybox Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 1.34.0-r0

alpine advisories ALPINE-CVE-2021-42375

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 Arch Linux 1.34.1-1
  • mkinitcpio-busybox Arch Linux 1.34.1-1

arch linux advisories AVG-2561AVG-2562

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-2021-42375 updated cvss 4.1

busybox: incorrect handling of a special element in ash applet leads to denial of service when processing a crafted shell command

  • 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 4.1

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 ICSA-23-075-01 updated cvss 4.1

Siemens SCALANCE, RUGGEDCOM Third-Party

  • Siemens RUGGEDCOM RM1224 LTE(4G) EU (6GK6108-4AM00-2BA2) <V7.2 Siemens RUGGEDCOM RM1224 LTE(4G) NAM (6GK6108-4AM00-2DA2) <V7.2 Siemens SCALANCE M804PB (6GK5804-0AP00-2AA2) <V7.2 Siemens SCALANCE M812-1 ADSL-Router (Annex A) (6GK5812-1AA00-2AA2) <V7.2 Siemens SCALANCE M812-1 ADSL-Router (Annex B) (6GK5812-1BA00-2AA2) <V7.2 Siemens SCALANCE M816-1 ADSL-Router (Annex A) (6GK5816-1AA00-2AA2) <V7.2
    +14 more products
    Siemens SCALANCE M816-1 ADSL-Router (Annex B) (6GK5816-1BA00-2AA2) <V7.2 Siemens SCALANCE M826-2 SHDSL-Router (6GK5826-2AB00-2AB2) <V7.2 Siemens SCALANCE M874-2 (6GK5874-2AA00-2AA2) <V7.2 Siemens SCALANCE M874-3 (6GK5874-3AA00-2AA2) <V7.2 Siemens SCALANCE M876-3 (EVDO) (6GK5876-3AA02-2BA2) <V7.2 Siemens SCALANCE M876-3 (ROK) (6GK5876-3AA02-2EA2) <V7.2 Siemens SCALANCE M876-4 (6GK5876-4AA10-2BA2) <V7.2 Siemens SCALANCE M876-4 (EU) (6GK5876-4AA00-2BA2) <V7.2 Siemens SCALANCE M876-4 (NAM) (6GK5876-4AA00-2DA2) <V7.2 Siemens SCALANCE MUM853-1 (EU) (6GK5853-2EA00-2DA1) <V7.2 Siemens SCALANCE MUM856-1 (EU) (6GK5856-2EA00-3DA1) <V7.2 Siemens SCALANCE MUM856-1 (RoW) (6GK5856-2EA00-3AA1) <V7.2 Siemens SCALANCE S615 (6GK5615-0AA00-2AA2) <V7.2 Siemens SCALANCE S615 EEC (6GK5615-0AA01-2AA2) <V7.2
    affected: fixed in V7.2 support.industry.siemens.com

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

cisa ICSA-23-080-07 updated cvss 4.1

Siemens SCALANCE Third-Party

  • Siemens SCALANCE WAM763-1 (6GK5763-1AL00-7DA0) <V2.0 Siemens SCALANCE WAM766-1 (EU) (6GK5766-1GE00-7DA0) <V2.0 Siemens SCALANCE WAM766-1 (US) (6GK5766-1GE00-7DB0) <V2.0 Siemens SCALANCE WAM766-1 EEC (EU) (6GK5766-1GE00-7TA0) <V2.0 Siemens SCALANCE WAM766-1 EEC (US) (6GK5766-1GE00-7TB0) <V2.0 Siemens SCALANCE WUM763-1 (6GK5763-1AL00-3AA0) <V2.0
    +3 more products
    Siemens SCALANCE WUM763-1 (6GK5763-1AL00-3DA0) <V2.0 Siemens SCALANCE WUM766-1 (EU) (6GK5766-1GE00-3DA0) <V2.0 Siemens SCALANCE WUM766-1 (US) (6GK5766-1GE00-3DB0) <V2.0
    affected: fixed in V2.0 support.industry.siemens.com

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
18 mo ago

Exploit prediction

0.41% chance of exploitation in the next 30 days, higher than 35% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 1.9 AV:L/AC:M/Au:N/C:N/I:N/A:P

Affected products

  • busybox busybox

Classification

Weakness
  • CWE-159 Improper Handling of Invalid Use of Special Elements

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.