How severe is CVE-2021-43797?

CVE-2021-43797 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-43797 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43797?

CVE-2021-43797 primarily affects Netty. In total, 22 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-43797?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-43797 published?

CVE-2021-43797 was published on 2021-12-09 and last updated on 2026-06-17.

CVE-2021-43797

CVE-2021-43797 is a medium-severity vulnerability in Netty with a CVSS 3.x base score of 6.5. 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-444.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.3
EPSS exploit prediction: 3% (84th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-444
Affected product: Netty
Published: 2021-12-09
Last modified: 2026-06-17

Description

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. Netty prior to version 4.1.71.Final skips control chars when they are present at the beginning / end of the header name. It should instead fail fast as these are not allowed by the spec and could lead to HTTP request smuggling. Failing to do the validation might cause netty to "sanitize" header names before it forward these to another remote system when used as proxy. This remote system can't see the invalid usage anymore, and therefore does not do the validation itself. Users should upgrade to version 4.1.71.Final.

Frequently asked questions

What is CVE-2021-43797?: Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. Netty prior to version 4.1.71.Final skips control chars when they are present at the beginning / end of the header name. It should instead fail fast as these are not allowed by the spec and could lead to HTTP request smuggling. Failing to do the validation might cause netty to "sanitize" header names before it forward these to another remote system when used as proxy. This remote system can't see the invalid usage anymore, and therefore does not do the validation itself. Users should upgrade to version 4.1.71.Final.
How severe is CVE-2021-43797?: CVE-2021-43797 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-43797 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43797?: CVE-2021-43797 primarily affects Netty. In total, 22 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-43797?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-43797 published?: CVE-2021-43797 was published on 2021-12-09 and last updated on 2026-06-17.

References

Affected products (22)

cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*
cpe:2.3:a:quarkus:quarkus:*:*:*:*:*:*:*:*
cpe:2.3:a:netapp:oncommand_workflow_automation:-:*:*:*:*:*:*:*
cpe:2.3:a:netapp:snapcenter:-:*:*:*:*:*:*:*
cpe:2.3:a:oracle:banking_deposits_and_lines_of_credit_servicing:2.7:*:*:*:*:*:*:*
cpe:2.3:a:oracle:banking_party_management:2.7.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:banking_platform:2.6.2:*:*:*:*:*:*:*
cpe:2.3:a:oracle:coherence:12.2.1.4.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:coherence:14.1.1.0.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_binding_support_function:1.11.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_network_slice_selection_function:1.8.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_policy:1.15.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_security_edge_protection_proxy:1.7.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_cloud_native_core_unified_data_repository:1.15.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_design_studio:7.4.2:*:*:*:*:*:*:*
cpe:2.3:a:oracle:communications_instant_messaging_server:8.1:*:*:*:*:*:*:*
cpe:2.3:a:oracle:helidon:1.4.10:*:*:*:*:*:*:*
cpe:2.3:a:oracle:helidon:2.4.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.58:*:*:*:*:*:*:*
cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.59:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

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