CVE-2021-42377

An attacker-controlled pointer free in Busybox's hush applet leads to denial of service and possible code execution when processing a crafted shell command, due to the shell mishandling the &&& string. This may be used for remote code execution under rare conditions of filtered command input.

Published: 2021-11-15 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-42377 is rated High Risk (70.2/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 3.38%). High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-42377

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 2.85% 3.38% +0.52%
2 2026-01-14 1.86% 2.85% +1.00%
3 2025-11-21 — 1.86% —

Full EPSS history (27 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-42377

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
6.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 6.4 [email protected]

Weakness enumeration for CVE-2021-42377

OS Trackers for CVE-2021-42377

vendor priority summary link
alpine critical CVE-2021-42377: 1 source package rows (busybox); 5 state rows across 5 repos (3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 5, open 0. https://security.alpinelinux.org/vuln/CVE-2021-42377
debian unimportant CVE-2021-42377 unimportant priority: Debian including 1 source packages (busybox), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1. https://security-tracker.debian.org/tracker/CVE-2021-42377
gentoo normal CVE-2021-42377: 1 GLSA(s) (202407-17), 1 atom(s) (sys-apps/busybox); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-42377
redhat medium — https://access.redhat.com/security/cve/CVE-2021-42377
suse medium CVE-2021-42377 severity moderate: SUSE including 24 source package names (1.34.1:busybox-1.34.1-4.9.1, 15.4:busybox-1.35.0-150400.3.3.1, …), 84 product×package rows across 52 product lines (Container bci/bci-busybox, Container caasp/v4/busybox, … (52 product lines)): Fixed 77, Known Not Affected 7. https://www.suse.com/security/cve/CVE-2021-42377/
ubuntu low CVE-2021-42377 low priority: Ubuntu including 1 source packages (busybox), 8 status rows across 8 suites (bionic, focal, hirsute, impish, jammy, trusty, upstream, xenial): not-affected 7, released 1. https://ubuntu.com/security/CVE-2021-42377

Affected software / configurations for CVE-2021-42377

Vendor Product Version Raw CPE
busybox busybox 1.33.0 cpe:2.3:a:busybox:busybox:1.33.0:*:*:*:*:*:*:*
busybox busybox 1.33.1 cpe:2.3:a:busybox:busybox:1.33.1:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
netapp cloud_backup — cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*
netapp hci_management_node — cpe:2.3:a:netapp:hci_management_node:-:*:*:*:*:*:*:*
netapp solidfire — cpe:2.3:a:netapp:solidfire:-:*:*:*:*:*:*:*
netapp h300s_firmware — cpe:2.3:o:netapp:h300s_firmware:-:*:*:*:*:*:*:*
netapp h500s_firmware — cpe:2.3:o:netapp:h500s_firmware:-:*:*:*:*:*:*:*
netapp h700s_firmware — cpe:2.3:o:netapp:h700s_firmware:-:*:*:*:*:*:*:*
netapp h300e_firmware — cpe:2.3:o:netapp:h300e_firmware:-:*:*:*:*:*:*:*
netapp h500e_firmware — cpe:2.3:o:netapp:h500e_firmware:-:*:*:*:*:*:*:*
netapp h700e_firmware — cpe:2.3:o:netapp:h700e_firmware:-:*:*:*:*:*:*:*
netapp h410s_firmware — cpe:2.3:o:netapp:h410s_firmware:-:*:*:*:*:*:*:*

References for CVE-2021-42377

cvelogic Threat Intelligence