How severe is CVE-2026-42581?

CVE-2026-42581 has a CVSS 3.x base score of 5.8, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2026-42581 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (40th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42581?

CVE-2026-42581 affects Netty. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-42581?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-42581 have an EU (EUVD) identifier?

Yes. CVE-2026-42581 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30124.

When was CVE-2026-42581 published?

CVE-2026-42581 was published on 2026-05-13 and last updated on 2026-06-30.

CVE-2026-42581

CVE-2026-42581 is a medium-severity vulnerability in Netty with a CVSS 3.x base score of 5.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-444.

Key facts

Severity: Medium (CVSS 3.x base score 5.8)
EPSS exploit prediction: 1% (40th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30124
Weakness: CWE-444
Affected product: Netty
Published: 2026-05-13
Last modified: 2026-06-30

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.

Frequently asked questions

What is CVE-2026-42581?: 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.
How severe is CVE-2026-42581?: CVE-2026-42581 has a CVSS 3.x base score of 5.8, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2026-42581 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (40th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42581?: CVE-2026-42581 affects Netty. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-42581?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-42581 have an EU (EUVD) identifier?: Yes. CVE-2026-42581 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30124.
When was CVE-2026-42581 published?: CVE-2026-42581 was published on 2026-05-13 and last updated on 2026-06-30.

References

Affected products (1)

cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*

More vulnerabilities in Netty

CVE-2019-20445 — Critical (CVSS 9.1): HttpObjectDecoder.java in Netty before 4.1.44 allows a Content-Length header to be accompanied by a second…
CVE-2019-20444 — Critical (CVSS 9.1): HttpObjectDecoder.java in Netty before 4.1.44 allows an HTTP header that lacks a colon, which might be interpreted as a…
CVE-2026-47691 — High (CVSS 8.7): Netty is a network application framework for development of protocol servers and clients. Prior to versions…
CVE-2026-45674 — High (CVSS 8.7): Netty is a network application framework for development of protocol servers and clients. Prior to versions…
CVE-2026-44249 — High (CVSS 8.1): Netty is a network application framework for development of protocol servers and clients. In netty-handler prior to…
CVE-2026-50011 — High (CVSS 7.5): Netty is a network application framework for development of protocol servers and clients. Prior to versions…

All CVEs affecting Netty →

Other CWE-444 (HTTP Request/Response Smuggling) vulnerabilities

CVE-2025-1867 — Critical (CVSS 10.0): Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in ithewei libhv allows…
CVE-2022-22536 — Critical (CVSS 10.0): SAP NetWeaver Application Server ABAP, SAP NetWeaver Application Server Java, ABAP Platform, SAP Content Server 7.53…
CVE-2018-3907 — Critical (CVSS 10.0): An exploitable vulnerability exists in the REST parser of video-core's HTTP server of the Samsung SmartThings Hub…
CVE-2025-55315 — Critical (CVSS 9.9): Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an authorized…
CVE-2020-15049 — Critical (CVSS 9.9): An issue was discovered in http/ContentLengthInterpreter.cc in Squid before 4.12 and 5.x before 5.0.3. A Request…
CVE-2026-13763 — Critical (CVSS 9.8): Inconsistent interpretation of HTTP/2 requests in AWS Application Load Balancer with AWS WAF enabled might allow remote…

Browse all CWE-444 (HTTP Request/Response Smuggling) vulnerabilities →