Is CVE-2021-21409 in the CISA KEV catalog?

No. CVE-2021-21409 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-21409?

CVE-2021-21409 has a CVSS v3 base score of 5.9 (MEDIUM).

What is the EPSS score for CVE-2021-21409?

CVE-2021-21409 has an EPSS score of 4.93% (91th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-21409?

Upgrade netty on debian 11 to 1:4.1.48-4 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2021-21409

MEDIUMEPSS 91th pctl

5.9

CVSS v3

NVD

Description

Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. In Netty (io.netty:netty-codec-http2) before version 4.1.61.Final there is a vulnerability that enables request smuggling. The content-length header is not correctly validated if the request only uses a single Http2HeaderFrame with the endStream set to to true. This could lead to request smuggling if the request is proxied to a remote peer and translated to HTTP/1.1. This is a followup of GHSA-wm47-8v5p-wjpj/CVE-2021-21295 which did miss to fix this one case. This was fixed as part of 4.1.61.Final.

CWE-444

How to fix

Remediation Available

nettyDebian

Fixed in:1:4.1.48-4CVE-2021-21409

libnetty-javaUbuntu

Fixed in:1:4.0.34-1ubuntu0.1~esm1USN-6049-1

Fixed in:1:4.1.7-4ubuntu0.1+esm2USN-6049-1

Fixed in:1:4.1.45-1ubuntu0.1~esm1USN-6049-1

Fixed in:1:4.1.48-4+deb11u1build0.22.04.1USN-6049-1

Fixed in:1:4.1.48-5ubuntu0.1USN-6049-1

nettyUbuntu

Fixed in:1:4.0.34-1ubuntu0.1~esm1USN-6049-1

Fixed in:1:4.1.7-4ubuntu0.1+esm2USN-6049-1

Fixed in:1:4.1.45-1ubuntu0.1~esm1USN-6049-1

Fixed in:1:4.1.48-4+deb11u1build0.22.04.1USN-6049-1

Fixed in:1:4.1.48-5ubuntu0.1USN-6049-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Exploit Intelligence

4.93%probability of exploitation in 30 days

91stpercentile

High risk: more likely to be exploited than 91% of all known CVEs.

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.