Netty's HttpServerCodec (io.netty:netty-codec-http) in versions 4.2.0.Final through 4.2.16.Final and in versions up to and including 4.1.136.Final pairs each outbound response with an inbound request by calling pollMethod() once per response, including for 1xx informational responses. If a client pipelines an HTTP/1.1 GET carrying an Expect: 100-continue header followed by a HEAD request, the 100 Continue response consumes the queued GET method, so the subsequent 200 OK for the GET is paired with HEAD and its body is dropped, while the following 200 OK for the HEAD request is written with a body. This desynchronizes HTTP parsing on the connection: the GET entity is never delivered and the HEAD response body is interpreted as the GET body, resulting in response splitting and unsafe connection reuse. Fixed in 4.2.17.Final and 4.1.137.Final.
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Affected Vendors & Products
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Fixes
Solution
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Workaround
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References
History
Sat, 26 Sep 2026 13:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | Netty's HttpServerCodec (io.netty:netty-codec-http) in versions 4.2.0.Final through 4.2.16.Final and in versions up to and including 4.1.136.Final pairs each outbound response with an inbound request by calling pollMethod() once per response, including for 1xx informational responses. If a client pipelines an HTTP/1.1 GET carrying an Expect: 100-continue header followed by a HEAD request, the 100 Continue response consumes the queued GET method, so the subsequent 200 OK for the GET is paired with HEAD and its body is dropped, while the following 200 OK for the HEAD request is written with a body. This desynchronizes HTTP parsing on the connection: the GET entity is never delivered and the HEAD response body is interpreted as the GET body, resulting in response splitting and unsafe connection reuse. Fixed in 4.2.17.Final and 4.1.137.Final. | |
| Title | Netty 4.2.0 through 4.2.17 Response Desynchronization via HttpServerCodec | |
| First Time appeared |
Netty
Netty netty |
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| Weaknesses | CWE-444 | |
| CPEs | cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Netty
Netty netty |
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| References |
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| Metrics |
cvssV3_1
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MITRE
Status: PUBLISHED
Assigner: VulnCheck
Published:
Updated: 2026-09-26T13:23:31.961Z
Reserved: 2026-09-26T02:34:55.634Z
Link: CVE-2026-100666
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-26T14:16:49.830
Modified: 2026-09-26T14:16:49.830
Link: CVE-2026-100666
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses