CVE-2026-59900

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

MEDIUM

5.3

CVSS Score

Published: July 29, 2026 at 05:58 PM UTC

Updated: August 6, 2026 at 08:40 PM UTC

1 product affected across 1 vendorNetty

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Severity

MEDIUM5.3

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

Description

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, 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. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Netty · Nettymaven

95%

v < 4.1.136v < 4.1.136.Finalv < 4.2.16.Final4.2.0 ≤ v < 4.2.16

Affected range stops below 4.1.136, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.1.136.Final, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.2.16, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.2.16.Final, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://github.com/netty/netty/security/advisories/GHSA-c69g-56f8-xwqj

References (3)

x_refsource_CONFIRMVendor Advisory

Source: cverecord

https://github.com/netty/netty/security/advisories/GHSA-c69g-56f8-xwqj

x_refsource_MISCRelease Notes

Source: cverecord

https://github.com/netty/netty/releases/tag/netty-4.1.136.Final

x_refsource_MISCRelease Notes

Source: cverecord

https://github.com/netty/netty/releases/tag/netty-4.2.16.Final

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUM[email protected]

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: LOW
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-444

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