CVE-2021-43797 | HTTP fails to validate against control chars in header names which may lead to HTTP request smuggling

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.

Published: 2021-12-09 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-43797 is rated Moderate Risk (46.8/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.38%). Review affected assets and schedule 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-2021-43797

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 2026-03-04 0.21% 0.38% +0.17%
2 2026-03-01 0.42% 0.21% -0.21%
3 2026-02-04 — 0.42% —

Full EPSS history (34 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-43797

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N 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:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 3.6 [email protected]
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N 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:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 3.6 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N 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:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-43797

GitHub Security Advisory for CVE-2021-43797

GHSA-wx5j-54mm-rqqq · Severity: medium · Ecosystem: maven — HTTP request smuggling in netty

OS Trackers for CVE-2021-43797

vendor priority summary link
debian not yet assigned CVE-2021-43797 not yet assigned priority: Debian including 1 source packages (netty), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-43797
redhat medium — https://access.redhat.com/security/cve/CVE-2021-43797
suse medium CVE-2021-43797 severity moderate: SUSE including 13 source package names (5.0.0-beta1.2.122:netty-4.1.75-150200.4.6.2, 5.1.0.6.40:netty-4.1.75-150200.4.6.2, …), 34 product×package rows across 22 product lines (Container suse/manager/5.0/x86_64/server, Container suse/multi-linux-manager/5.1/x86_64/server, … (22 product lines)): Fixed 31, Known Not Affected 3. https://www.suse.com/security/cve/CVE-2021-43797/
ubuntu medium CVE-2021-43797 medium priority: Ubuntu including 1 source packages (netty), 15 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): released 10, ignored 4, needs-triage 1. https://ubuntu.com/security/CVE-2021-43797

Affected software / configurations for CVE-2021-43797

Vendor Product Version Raw CPE
netty netty < 4.1.71 cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*
quarkus quarkus < 2.5.3 cpe:2.3:a:quarkus:quarkus:*:*:*:*:*:*:*:*
netapp oncommand_workflow_automation — cpe:2.3:a:netapp:oncommand_workflow_automation:-:*:*:*:*:*:*:*
netapp snapcenter — cpe:2.3:a:netapp:snapcenter:-:*:*:*:*:*:*:*
oracle banking_deposits_and_lines_of_credit_servicing 2.7 cpe:2.3:a:oracle:banking_deposits_and_lines_of_credit_servicing:2.7:*:*:*:*:*:*:*
oracle banking_party_management 2.7.0 cpe:2.3:a:oracle:banking_party_management:2.7.0:*:*:*:*:*:*:*
oracle banking_platform 2.6.2 cpe:2.3:a:oracle:banking_platform:2.6.2:*:*:*:*:*:*:*
oracle coherence 12.2.1.4.0 cpe:2.3:a:oracle:coherence:12.2.1.4.0:*:*:*:*:*:*:*
oracle coherence 14.1.1.0.0 cpe:2.3:a:oracle:coherence:14.1.1.0.0:*:*:*:*:*:*:*
oracle communications_cloud_native_core_binding_support_function 1.11.0 cpe:2.3:a:oracle:communications_cloud_native_core_binding_support_function:1.11.0:*:*:*:*:*:*:*
oracle communications_cloud_native_core_network_slice_selection_function 1.8.0 cpe:2.3:a:oracle:communications_cloud_native_core_network_slice_selection_function:1.8.0:*:*:*:*:*:*:*
oracle communications_cloud_native_core_policy 1.15.0 cpe:2.3:a:oracle:communications_cloud_native_core_policy:1.15.0:*:*:*:*:*:*:*
oracle communications_cloud_native_core_security_edge_protection_proxy 1.7.0 cpe:2.3:a:oracle:communications_cloud_native_core_security_edge_protection_proxy:1.7.0:*:*:*:*:*:*:*
oracle communications_cloud_native_core_unified_data_repository 1.15.0 cpe:2.3:a:oracle:communications_cloud_native_core_unified_data_repository:1.15.0:*:*:*:*:*:*:*
oracle communications_design_studio 7.4.2 cpe:2.3:a:oracle:communications_design_studio:7.4.2:*:*:*:*:*:*:*
oracle communications_instant_messaging_server 8.1 cpe:2.3:a:oracle:communications_instant_messaging_server:8.1:*:*:*:*:*:*:*
oracle helidon 1.4.10 cpe:2.3:a:oracle:helidon:1.4.10:*:*:*:*:*:*:*
oracle helidon 2.4.0 cpe:2.3:a:oracle:helidon:2.4.0:*:*:*:*:*:*:*
oracle peoplesoft_enterprise_peopletools 8.58 cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.58:*:*:*:*:*:*:*
oracle peoplesoft_enterprise_peopletools 8.59 cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.59:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

References for CVE-2021-43797

cvelogic Threat Intelligence