CVE-2026-42581
Published: 13 May 2026
Summary
CVE-2026-42581 is a medium-severity HTTP Request/Response Smuggling (CWE-444) vulnerability in Netty Netty. Its CVSS base score is 5.8 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 40.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-30124
Vulnerability details
Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-Length, but only for HTTP/1.1 messages. The guard is absent for HTTP/1.0. An…
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attacker that sends an HTTP/1.0 request with both headers causes Netty to decode the body as chunked while leaving Content-Length intact in the forwarded HttpMessage. Any downstream proxy or handler that trusts Content-Length over Transfer-Encoding will disagree on message boundaries, enabling request smuggling. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
HTTP/1.0 request smuggling due to inconsistent Content-Length/Transfer-Encoding handling in public Netty HTTP framework directly enables exploitation of public-facing applications.
Affected Assets
Mitigating Controls
No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.