How severe is CVE-2021-43396?

CVE-2021-43396 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-43396 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43396?

CVE-2021-43396 primarily affects Gnu Glibc. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-43396?

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

When was CVE-2021-43396 published?

CVE-2021-43396 was published on 2021-11-04 and last updated on 2026-06-17.

CVE-2021-43396

CVE-2021-43396 is a high-severity vulnerability in Gnu Glibc with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 3% (85th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Gnu Glibc
Published: 2021-11-04
Last modified: 2026-06-17

Description

In iconvdata/iso-2022-jp-3.c in the GNU C Library (aka glibc) 2.34, remote attackers can force iconv() to emit a spurious '\0' character via crafted ISO-2022-JP-3 data that is accompanied by an internal state reset. This may affect data integrity in certain iconv() use cases. NOTE: the vendor states "the bug cannot be invoked through user input and requires iconv to be invoked with a NULL inbuf, which ought to require a separate application bug to do so unintentionally. Hence there's no security impact to the bug.

Frequently asked questions

What is CVE-2021-43396?: In iconvdata/iso-2022-jp-3.c in the GNU C Library (aka glibc) 2.34, remote attackers can force iconv() to emit a spurious '\0' character via crafted ISO-2022-JP-3 data that is accompanied by an internal state reset. This may affect data integrity in certain iconv() use cases. NOTE: the vendor states "the bug cannot be invoked through user input and requires iconv to be invoked with a NULL inbuf, which ought to require a separate application bug to do so unintentionally. Hence there's no security impact to the bug.
How severe is CVE-2021-43396?: CVE-2021-43396 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-43396 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43396?: CVE-2021-43396 primarily affects Gnu Glibc. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-43396?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-43396 published?: CVE-2021-43396 was published on 2021-11-04 and last updated on 2026-06-17.

References

Affected products (10)

cpe:2.3:a:gnu:glibc:2.34:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_binding_support_function:22.1.3:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_network_function_cloud_native_environment:22.1.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_network_repository_function:22.1.2:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_network_repository_function:22.2.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_security_edge_protection_proxy:22.1.1:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_unified_data_repository:22.2.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:enterprise_operations_monitor:4.3:*:*:*:*:*:*:*
cpe:2.3:a:oracle:enterprise_operations_monitor:4.4:*:*:*:*:*:*:*
cpe:2.3:a:oracle:enterprise_operations_monitor:5.0:*:*:*:*:*:*:*

More vulnerabilities in Gnu Glibc

CVE-2015-0235 — Critical (CVSS 10.0): Heap-based buffer overflow in the __nss_hostname_digits_dots function in glibc 2.2, and other 2.x versions before 2.18,…
CVE-2026-5450 — Critical (CVSS 9.8): Calling the scanf family of functions with a %mc (malloc'd character match) in the GNU C Library version 2.7 to version…
CVE-2023-25139 — Critical (CVSS 9.8): sprintf in the GNU C Library (glibc) 2.37 has a buffer overflow (out-of-bounds write) in some situations with a correct…
CVE-2022-23219 — Critical (CVSS 9.8): The deprecated compatibility function clnt_create in the sunrpc module of the GNU C Library (aka glibc) through 2.34…
CVE-2022-23218 — Critical (CVSS 9.8): The deprecated compatibility function svcunix_create in the sunrpc module of the GNU C Library (aka glibc) through 2.34…
CVE-2021-33574 — Critical (CVSS 9.8): The mq_notify function in the GNU C Library (aka glibc) versions 2.32 and 2.33 has a use-after-free. It may use the…

All CVEs affecting Gnu Glibc →