THREATPORT/VULNERABILITY/CVE-2021-21409
MEDIUM SEVERITY

CVE-2021-21409

Netty vulnerability

CVSS
5.9
EPSS
4.9%
EPSS pct
91th
Exploited
No known
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.
Affected vendor
Netty
Affected product
Netty
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness type (CWE)
Published
2021-03-30

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, high attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to integrity.

Its EPSS score of 4.9% reflects a lower probability of exploitation activity in the wild over the next 30 days, placing it above 91% of all scored CVEs.

Check your external exposure to CVE-2021-21409

  • Confirm whether Netty Netty is running on any internet-facing host or subdomain.
  • Match discovered service fingerprints against the version affected by CVE-2021-21409.
  • Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2021-21409

ThreatPort's external attack surface scanner checks your internet-facing assets — agentlessly, from the outside in — for the exposed services and versions that CVE-2021-21409 affects, then prioritises the finding by real risk using CISA KEV and FIRST.org EPSS.

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