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Medium

Possible request smuggling in HTTP/2 due missing validation of content-length

  • Disclosed: 30.03.2021
  • Updated: 11.10.2026 13:19

Impact

The content-length header is not correctly validated if the request only use 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 https://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj which did miss to fix this one case.

Patches

This was fixed as part of 4.1.61.Final

Workarounds

Validation can be done by the user before proxy the request by validating the header.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Java / Kotlin (Maven) io.netty:netty all versions no fix
Java / Kotlin (Maven) io.netty:netty-codec-http2 >= 4.0.0, < 4.1.61.Final 4.1.61.Final
Java / Kotlin (Maven) org.jboss.netty:netty all versions no fix

References

CVSS score 5.9/10
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness (CWE)
CWE-444
Platform
Java / Kotlin (Maven)
Package
io.netty:netty, io.netty:netty-codec-http2, org.jboss.netty:netty
Disclosed
30.03.2021
Updated
11.10.2026 13:19

Sources and licenses

OSV / GitHub Advisory Database - GHSA-f256-j965-7f32 - CC BY 4.0

Vulnerability history: io.netty:netty

All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (11) in the archive
Total entries
11
First → latest
10.2019 05.2022
Without a fix
9
Exploited in attacks
0

Severity breakdown

  • Critical 1
  • High 4
  • Medium 6

Disclosures per year

Severity:
  1. SnappyFrameDecoder doesn't restrict chunk length any may buffer skippable chunks in an unnecessary way
    High · 7.5 CVE-2021-37137 all versions no fix
  2. Bzip2Decoder doesn't allow setting size restrictions for decompressed data
    High · 7.5 CVE-2021-37136 all versions no fix
  3. Possible request smuggling in HTTP/2 due missing validation of content-length this entry
    Medium · 5.9 CVE-2021-21409 all versions no fix
  4. Information Exposure in Netty
    High · 7.5 CVE-2015-2156 >= 3.10.0, < 3.10.3.Final, < 3.9.8.Final 3.10.3.Final, 3.9.8.Final
  5. HTTP Request Smuggling in Netty
    Critical · 9.1 CVE-2019-20444 all versions no fix
  6. HTTP Request Smuggling in Netty
    High · 7.5 CVE-2019-16869 >= 3.3.0.Final, <= 4.0.0.Alpha8 no fix

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