CVE-2026-42581Netty is an asynchronous, event-driven network application framework.
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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.
- CVSS
- 9.8 CRITICAL (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-444
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Sep 18, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
netty netty netty:netty | before 4.1.133; from 4.2.0 before 4.2.13 | NVD |
References
- https://github.com/netty/netty/security/advisories/GHSA-xxqh-mfjm-7mv9exploit, mitigation, vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:23808
- https://access.redhat.com/errata/RHSA-2026:24502
- https://access.redhat.com/errata/RHSA-2026:25123
- https://access.redhat.com/errata/RHSA-2026:28010
- https://access.redhat.com/errata/RHSA-2026:36820
- https://access.redhat.com/errata/RHSA-2026:37390
- https://access.redhat.com/errata/RHSA-2026:42644
- https://access.redhat.com/errata/RHSA-2026:49700
- https://access.redhat.com/errata/RHSA-2026:49701
- https://access.redhat.com/errata/RHSA-2026:53644
- https://access.redhat.com/errata/RHSA-2026:53645
- https://access.redhat.com/errata/RHSA-2026:53646
- https://access.redhat.com/errata/RHSA-2026:54435
- https://access.redhat.com/errata/RHSA-2026:65126
- https://access.redhat.com/errata/RHSA-2026:66488
- https://access.redhat.com/errata/RHSA-2026:66545
- https://access.redhat.com/security/cve/CVE-2026-42581
- https://bugzilla.redhat.com/show_bug.cgi?id=2477232
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42581.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.