CVE-2026-42581: netty · HTTP Request Smuggling
Affects nettySource GCVE Database
Not known to be exploited · CVSS 5.8 Medium : upgrade to 4.2.13.Final or 4.1.133.Final when convenient.
Data as of 11 Nov 2026, 23:24 UTC
Sources agree
| CNA (GitHub_M) | CVSS 3.1 | 5.8 |
|---|---|---|
| ADP (redhat-SADP) | CVSS 3.1 | 7.2 |
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 4.2.13.Final, 4.1.133.Final
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 13 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.
What to do
Upgrade netty to 4.2.13.Final or 4.1.133.Final.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| netty netty | Affected
| Fixed in
|
Description
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.
References
- github.com/netty/netty/security/advisories/GHSA-xxqh-mfjm-7mv9 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-42581 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2477232 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42581.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:49700 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:53644 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:53645 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:28010 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:53646 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:66545 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:66488 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:49701 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:42644 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65126 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:25123 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36820 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:37390 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:23808 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:24502 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54435 (opens in a new tab)