VulnerabilityPublished 13 May 2026Updated 18 Sep 2026

CVE-2026-42584: netty · HTTP Request/Response Smuggling

Affects nettySource GCVE Database

Not known to be exploited · CVSS 7.3 High : upgrade to 4.2.13.Final or 4.1.133.Final soon.

Data as of 26 Oct 2026, 18:26 UTC

CVSS 3.1 base score

7.3High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 4.2.13.Final, 4.1.133.Final

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade netty to 4.2.13.Final or 4.1.133.Final.

Affected software

Product	Affected	Fixed in
netty netty	Affected >=4.2.0.Alpha1 <4.2.13.Final <4.1.133.Final	Fixed in 4.2.13.Final 4.1.133.Final

AI-suggested

This vulnerability is fixed in Netty versions 4.2.13.Final and 4.1.133.Final. Users and vendors should upgrade to these or later versions to remediate the issue.

Description

CVE-2026-42584 is a vulnerability in Netty's HttpClientCodec where certain sequences of HTTP responses cause incorrect pairing of responses to requests. This leads to subsequent HTTP responses being parsed from incorrect offsets, potentially causing information disclosure or data integrity issues. The flaw is fixed in Netty versions 4.2.13.Final and 4.1.133.Final.

Impact

The vulnerability allows a remote attacker to cause misinterpretation of HTTP responses by sending a crafted sequence of HTTP responses. This can lead to information disclosure or data integrity issues in applications using Netty's HTTP client functionality. The flaw affects multiple Red Hat products bundling Netty, including Red Hat AMQ, Enterprise Application Platform, Red Hat Build of Quarkus, and Red Hat Build of Keycloak.

Summary

Netty, an asynchronous event-driven network application framework, had a flaw in HttpClientCodec prior to versions 4.2.13.Final and 4.1.133.Final. When a client pipelines GET then HEAD requests and the server responds with a sequence of 103, then 200 with a GET body, then 200 for HEAD, the codec incorrectly pairs the HEAD response with the first 200 response. This causes the HEAD rule to skip reading the body of that message, leaving GET entity bytes on the stream. Consequently, the following 200 response is parsed from the wrong offset, leading to data confusion. This vulnerability is classified as CWE-444 (HTTP Request/Response Smuggling) and has a CVSS 3.1 base score of 7.3 (high severity).

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') (opens in a new tab)
Base weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
Implementation
Use a web server that employs a strict HTTP parsing procedure, such as Apache.
Implementation
Use only SSL communication.
Implementation
Terminate the client session after each request.
OWASP Cheat Sheets
REST Assessment (opens in a new tab)
REST Security (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V13.2.5 (opens in a new tab)
Attack patterns
HTTP Response Smuggling (opens in a new tab)
HTTP Request Smuggling (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 18:26 UTC

WeaknessesCWE-444

Technical details

References

Community reviews

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