CVE catalog

CVE-2021-42376

busybox affected and fixed versions

A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command, due to missing validation after a \x03 delimiter character. This may be used for DoS under very rare conditions of filtered command input.

Severity: Medium · CVSS 4.1CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
Published: Nov 9, 2021, 12:00:00 AM UTC
Source: [NVD] · [CVE record]
EPSS: 0.43% · Oct 27, 2026

Projects and upstream resources

[busybox][Source-reported homepage]

Reported versions and fixes

Each observation applies to its named package, distribution, and release. Distribution backports can fix a vulnerability while retaining an older upstream version number.

Distribution / release	Package	Version	Status	Source
Debiantrixie	busybox	`1:1.35.0-1`	FixedDistribution-reported fixed boundary	[CVE-2021-42376]
Debiantrixie	busybox	`1:1.37.0-6`	Fixed	[CVE-2021-42376]
Debiansid	busybox	`1:1.35.0-1`	FixedDistribution-reported fixed boundary	[CVE-2021-42376]
Debiansid	busybox	`1:1.38.0-3`	Fixed	[CVE-2021-42376]
Debianforky	busybox	`1:1.35.0-1`	FixedDistribution-reported fixed boundary	[CVE-2021-42376]
Debianforky	busybox	`1:1.38.0-3`	Fixed	[CVE-2021-42376]
Debianbookworm	busybox	`1:1.35.0-1`	FixedDistribution-reported fixed boundary	[CVE-2021-42376]
Debianbookworm	busybox	`1:1.35.0-4+deb12u1`	Fixed	[CVE-2021-42376]

Showing 8 fix observations. All 9 observations, including unknown and conflicting reports, are available below.

Provider details and historical evidence

Distribution / release	Package	Version	Status	Source
UnknownRelease not reported	busybox	`1:1.35.0-1`	UnknownSource applicability is not established	Provider not reported
Debianbookworm	busybox	`1:1.35.0-1`	FixedDistribution-reported fixed boundary	[CVE-2021-42376]
Debianbookworm	busybox	`1:1.35.0-4+deb12u1`	Fixed	[CVE-2021-42376]
Debianforky	busybox	`1:1.35.0-1`	FixedDistribution-reported fixed boundary	[CVE-2021-42376]
Debianforky	busybox	`1:1.38.0-3`	Fixed	[CVE-2021-42376]
Debiansid	busybox	`1:1.35.0-1`	FixedDistribution-reported fixed boundary	[CVE-2021-42376]
Debiansid	busybox	`1:1.38.0-3`	Fixed	[CVE-2021-42376]
Debiantrixie	busybox	`1:1.35.0-1`	FixedDistribution-reported fixed boundary	[CVE-2021-42376]
Debiantrixie	busybox	`1:1.37.0-6`	Fixed	[CVE-2021-42376]

Original provider fields

{
  "package_releases": [
    {
      "name": "busybox",
      "status": "fixed",
      "release": "sid",
      "version": "1:1.38.0-3"
    },
    {
      "name": "busybox",
      "status": "fixed",
      "release": "forky",
      "version": "1:1.38.0-3"
    },
    {
      "name": "busybox",
      "status": "fixed",
      "release": "trixie",
      "version": "1:1.37.0-6"
    },
    {
      "name": "busybox",
      "status": "fixed",
      "release": "bookworm",
      "version": "1:1.35.0-4+deb12u1"
    }
  ],
  "fixed_versions": [
    {
      "bug": 999567,
      "name": "busybox",
      "type": "source",
      "origin": null,
      "release": "sid",
      "urgency": "unimportant",
      "fixed_version": "1:1.35.0-1"
    },
    {
      "bug": 999567,
      "name": "busybox",
      "type": "source",
      "origin": null,
      "release": "forky",
      "urgency": "unimportant",
      "fixed_version": "1:1.35.0-1"
    },
    {
      "bug": 999567,
      "name": "busybox",
      "type": "source",
      "origin": null,
      "release": "trixie",
      "urgency": "unimportant",
      "fixed_version": "1:1.35.0-1"
    },
    {
      "bug": 999567,
      "name": "busybox",
      "type": "source",
      "origin": null,
      "release": "bookworm",
      "urgency": "unimportant",
      "fixed_version": "1:1.35.0-1"
    }
  ],
  "distribution_packages": [
    {
      "name": "busybox",
      "fixed_version": "1:1.35.0-1",
      "applicability_unknown": true
    }
  ]
}

[Debian bug #999567]

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

[busybox]Unknown
Source package: [busybox]
Details (2)
- 1:1.35.0-4+deb12u1+b1 · amd64 · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12
- 1:1.35.0-4+deb12u1+b1 · arm64 · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12
[busybox-static]Unknown
Source package: [busybox]
Details (2)
- 1:1.35.0-4+deb12u1+b1 · amd64 · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12
- 1:1.35.0-4+deb12u1+b1 · arm64 · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12
[busybox-syslogd]Unknown
Source package: [busybox]
Details (2)
- 1:1.35.0-4+deb12u1 · all · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12
- 1:1.35.0-4+deb12u1 · all · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12
[udhcpc]Unknown
Source package: [busybox]
Details (2)
- 1:1.35.0-4+deb12u1+b1 · amd64 · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12
- 1:1.35.0-4+deb12u1+b1 · arm64 · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12
[udhcpd]Unknown
Source package: [busybox]
Details (2)
- 1:1.35.0-4+deb12u1+b1 · amd64 · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12
- 1:1.35.0-4+deb12u1+b1 · arm64 · bookworm
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · bookworm; dsa · busybox · debian · 12

[Debian 13 (Trixie)]

[busybox]Unknown
Source package: [busybox]
Details (2)
- 1:1.37.0-6+b8 · amd64 · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13
- 1:1.37.0-6+b8 · arm64 · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13
[busybox-static]Unknown
Source package: [busybox]
Details (2)
- 1:1.37.0-6+b8 · amd64 · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13
- 1:1.37.0-6+b8 · arm64 · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13
[busybox-syslogd]Unknown
Source package: [busybox]
Details (2)
- 1:1.37.0-6 · all · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13
- 1:1.37.0-6 · all · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13
[udhcpc]Unknown
Source package: [busybox]
Details (2)
- 1:1.37.0-6 · all · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13
- 1:1.37.0-6 · all · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13
[udhcpd]Unknown
Source package: [busybox]
Details (2)
- 1:1.37.0-6 · all · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13
- 1:1.37.0-6 · all · trixie
  Fixed · Fixed: 1:1.35.0-1
  dsa · busybox · debian · 13

Observed: Oct 23, 2026, 6:03:12 PM UTC

References

[CERT-Bund public advisories] · [CISA cybersecurity advisories] · [Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]