Response desynchronization via premature request dequeue
Published May 13, 2026 · Updated May 13, 2026
Response desynchronization in Netty HttpClientCodec before 4.1.133.Final and 4.2.13.Final allows remote attackers to misparse HTTP responses. HttpClientCodec removes one queued request for every response, including a 1xx interim response, so a pipelined HEAD request becomes associated with the preceding GET response and suppresses its body parsing. Exploitation requires HTTP/1.1 pipelining, a HEAD request in the pipeline, and a server-supplied 1xx response; leftover entity bytes are then parsed as the next response, allowing response data to cross request boundaries.
Summary
What happened
Response desynchronization in Netty HttpClientCodec before 4.1.133.Final and 4.2.13.Final allows remote attackers to misparse HTTP responses. HttpClientCodec removes one queued request for every response, including a 1xx interim response, so a pipelined HEAD request becomes associated with the preceding GET response and suppresses its body parsing. Exploitation requires HTTP/1.1 pipelining, a HEAD request in the pipeline, and a server-supplied 1xx response; leftover entity bytes are then parsed as the next response, allowing response data to cross request boundaries.
The record
- CVE
- CVE-2026-42584
- Published
- May 13, 2026
- Updated
- May 13, 2026
- Vendor
- The Netty Project
- Product
- Netty
- Classifications
- CWE-444, CAPEC-273
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 13, 2026CVE publishedPublication date reported by the CVE source.
- May 13, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 4.1.133.Final
- Affected versionversion=>= 4.2.0.Alpha1, < 4.2.13.Final
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- HttpClientCodec response desynchronization JUnit proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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