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Medium

Netty: [codec-http2] Lack of Host Header Deduplication in HTTP/2→HTTP/1.x Translation Leads to Request Routing Bypass

  • Disclosed: 22.07.2026
  • Updated: 11.10.2026 13:20

Netty's HTTP/2-to-HTTP/1.x translation layer (Http2StreamFrameToHttpObjectCodec and InboundHttp2ToHttpAdapter) fails to deduplicate or validate Host headers when an HTTP/2 client supplies both the :authority pseudo-header and a literal host header in a single HEADERS frame. The translator maps :authority to Host and separately copies the literal host header, producing an HttpRequest object containing two Host headers with attacker-controlled differing values.

Affected software

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PlatformPackageVulnerable versionsFixed in
Java / Kotlin (Maven) io.netty:netty-codec-http2 >= 4.2.0.Final, < 4.2.16.Final, < 4.1.136.Final 4.2.16.Final, 4.1.136.Final

References

CVSS score -
CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Weakness (CWE)
CWE-444
Platform
Java / Kotlin (Maven)
Package
io.netty:netty-codec-http2
Disclosed
22.07.2026
Updated
11.10.2026 13:20

Sources and licenses

OSV / GitHub Advisory Database - GHSA-c69g-56f8-xwqj - CC BY 4.0

Vulnerability history: io.netty:netty-codec-http2

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
03.2021 07.2026
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • High 5
  • Medium 6

Disclosures per year

Severity:
  1. Netty: HTTP/2 decompression leaks ByteBuf reference count when the decompressor channel is already closed (Direct memory leak / OOM DoS)
    High · 7.5 CVE-2026-56819 >= 4.2.0, < 4.2.16.Final, >= 4.1.0.Final, < 4.1.136.Final 4.2.16.Final, 4.1.136.Final
  2. Netty: [codec-http2] Lack of Host Header Deduplication in HTTP/2→HTTP/1.x Translation Leads to Request Routing Bypass this entry
    Medium CVE-2026-59900 >= 4.2.0.Final, < 4.2.16.Final, < 4.1.136.Final 4.2.16.Final, 4.1.136.Final
  3. Netty: HttpContentDecompressor maxAllocation bypass when Content-Encoding set to br/zstd/snappy leads to decompression bomb DoS
    High · 7.5 CVE-2026-42587 >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.Final 4.2.13.Final, 4.1.133.Final
  4. Netty HTTP/2 CONTINUATION Frame Flood DoS via Zero-Byte Frame Bypass
    High CVE-2026-33871 < 4.1.132.Final, >= 4.2.0.Alpha1, < 4.2.11.Final 4.1.132.Final, 4.2.11.Final
  5. Netty affected by MadeYouReset HTTP/2 DDoS vulnerability
    High · 7.5 CVE-2025-55163 >= 4.2.0.Alpha1, < 4.2.4.Final, < 4.1.124.Final 4.2.4.Final, 4.1.124.Final
  6. io.netty:netty-codec-http2 vulnerable to HTTP/2 Rapid Reset Attack
    High · 7.5 ghsa-xpw8-rcwv-8f8p < 4.1.100.Final 4.1.100.Final

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