CVSS 3.1
9.8 criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCVE-2026-42581
Critical (9.8) in netty netty. EPSS 0.6% chance of exploitation in the next 30 days. Fixed in io.netty:netty-codec-http 4.1.133.Final, 4.2.13.Final.
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 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.
Severity
- EPSS
- 0.6% chance of exploitation in the next 30 days; higher than 50% of CVEs (scores of 2026-10-31)
- CWE
- CWE-444
- Published
- Modified
- Record from
- the NVD, synced
Affected
- netty:netty
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-xxqh-mfjm-7mv9 | Maven | io.netty:netty-codec-http | >=4.2.0.Alpha1 <4.2.13.Final | 4.2.13.Final |
| GHSA-xxqh-mfjm-7mv9 | Maven | io.netty:netty-codec-http | <4.1.133.Final | 4.1.133.Final |