# CVE-2021-21295: Possible request smuggling in HTTP/2 due missing validation

Source: https://junglewise.ai/threats/cve-2021-21295-possible-request-smuggling-in-http-2-due-missing-validation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-03-09  
License: CC BY 4.0 with a link back

CVE-2021-21295 · Severity: low · CVSS 3.1 · Published 2021-03-09

Possible request smuggling in HTTP/2 due missing validation

Technologies: [io.netty:netty (Maven)](https://junglewise.ai/threats/technologies/io-netty-netty), [io.netty:netty-codec-http2 (Maven)](https://junglewise.ai/threats/technologies/io-netty-netty-codec-http2), [org.jboss.netty:netty (Maven)](https://junglewise.ai/threats/technologies/org-jboss-netty-netty). Vendors: [Maven](https://junglewise.ai/threats/vendors/maven).

## Quick answers

**Is CVE-2021-21295 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-21295 being exploited in the wild.

**How severe is CVE-2021-21295?** Low severity, with a CVSS score of 3.1, published 9 March 2021.

**Which products and versions are affected?** io.netty:netty (Maven) ECOSYSTEM:introduced=0; io.netty:netty-codec-http2 (Maven) ECOSYSTEM:introduced=4.0.0,fixed=4.1.60.Final; org.jboss.netty:netty (Maven) ECOSYSTEM:introduced=0.

**Is there a fix for CVE-2021-21295?** Yes. io.netty:netty-codec-http2 (Maven): upgrade to 4.1.60.Final or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-21295?** Check whether you run io.netty:netty (Maven), io.netty:netty-codec-http2 (Maven) or org.jboss.netty:netty (Maven) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- io.netty:netty-codec-http2 (Maven): upgrade to 4.1.60.Final or later

  ```sh
  # set io.netty:netty-codec-http2 to 4.1.60.Final in your pom.xml or build.gradle
  ```


## Affected products

- io.netty:netty (Maven) ECOSYSTEM:introduced=0
- io.netty:netty-codec-http2 (Maven) ECOSYSTEM:introduced=4.0.0,fixed=4.1.60.Final
- org.jboss.netty:netty (Maven) ECOSYSTEM:introduced=0

## Identifiers

- CVE-2021-21295
- GHSA-wm47-8v5p-wjpj

## Related threats

- [Netty request smuggling via Host header duplication in HTTP/2 translation](https://junglewise.ai/threats/cve-2026-59900-netty-request-smuggling-via-host-header-duplication-in-http-2)
- [Netty memory leak in HTTP/2 content decompression](https://junglewise.ai/threats/cve-2026-56819-netty-memory-leak-in-http-2-content-decompression)
- [Netty denial of service in HTTP/2 codec via max header size handling](https://junglewise.ai/threats/cve-2026-50560-netty-denial-of-service-in-http-2-codec-via-max-header-size)
- [Netty memory exhaustion in DelegatingDecompressorFrameListener](https://junglewise.ai/threats/cve-2026-48043-netty-memory-exhaustion-in-delegatingdecompressorframelistener)
- [Netty uncontrolled resource consumption in HTTP/2 codec](https://junglewise.ai/threats/cve-2026-47244-netty-uncontrolled-resource-consumption-in-http-2-codec)