How severe is CVE-2021-42377?

CVE-2021-42377 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-42377 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-42377?

CVE-2021-42377 primarily affects Busybox. In total, 14 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-42377?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-42377 published?

CVE-2021-42377 was published on 2021-11-15 and last updated on 2026-06-17.

CVE-2021-42377

CVE-2021-42377 is a critical-severity vulnerability in Busybox with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-763.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 6.8
EPSS exploit prediction: 3% (87th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-763
Affected product: Busybox
Published: 2021-11-15
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2021-42377?: CVE-2021-42377 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-42377 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-42377?: CVE-2021-42377 primarily affects Busybox. In total, 14 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-42377?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-42377 published?: CVE-2021-42377 was published on 2021-11-15 and last updated on 2026-06-17.

References

Affected products (14)

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

More vulnerabilities in Busybox

CVE-2022-48174 — Critical (CVSS 9.8): There is a stack overflow vulnerability in ash.c:6030 in busybox before 1.35. In the environment of Internet of…
CVE-2018-1000517 — Critical (CVSS 9.8): BusyBox project BusyBox wget version prior to commit 8e2174e9bd836e53c8b9c6e00d1bc6e2a718686e contains a Buffer…
CVE-2016-2148 — Critical (CVSS 9.8): Heap-based buffer overflow in the DHCP client (udhcpc) in BusyBox before 1.25.0 allows remote attackers to have…
CVE-2022-28391 — High (CVSS 8.8): BusyBox through 1.35.0 allows remote attackers to execute arbitrary code if netstat is used to print a DNS PTR record's…
CVE-2017-16544 — High (CVSS 8.8): In the add_match function in libbb/lineedit.c in BusyBox through 1.27.2, the tab autocomplete feature of the shell,…
CVE-2018-1000500 — High (CVSS 8.1): Busybox contains a Missing SSL certificate validation vulnerability in The "busybox wget" applet that can result in…

All CVEs affecting Busybox →

Other CWE-763 vulnerabilities

CVE-2026-52993 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: tipc: fix double-free in…
CVE-2025-14233 — Critical (CVSS 9.8): Invalid free in CPCA file deletion processing on Small Office Multifunction Printers and Laser Printers(*) which may…
CVE-2024-44852 — Critical (CVSS 9.8): Open Robotics Robotic Operating System 2 ROS2 navigation2 v.humble was discovered to contain a segmentation violation…
CVE-2021-30473 — Critical (CVSS 9.8): aom_image.c in libaom in AOMedia before 2021-04-07 frees memory that is not located on the heap.
CVE-2021-24028 — Critical (CVSS 9.8): An invalid free in Thrift's table-based serialization can cause the application to crash or potentially result in code…
CVE-2020-0103 — Critical (CVSS 9.8): In a2dp_aac_decoder_cleanup of a2dp_aac_decoder.cc, there is a possible invalid free due to memory corruption. This…

Browse all CWE-763 vulnerabilities →