Secuno
ENNL
Book demo

CVE-2026-42578

Netty vulnerability

7.5 HIGHPublic exploitEPSS 1.15%
  1. Published13 May 2026

Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Netty's HttpProxyHandler constructs HTTP CONNECT requests with header validation explicitly disabled. The newInitialMessage() method creates headers using DefaultHttpHeadersFactory.headersFactory().withValidation(false), then adds user-provided outboundHeaders without any CRLF validation. This allows an attacker who can influence the outbound headers to inject arbitrary HTTP headers into the CONNECT request sent to the proxy server. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected products

Netty≥ 4.2.0 < 4.2.13 · < 4.1.133

Remediation

Fixed in
Netty≥ 4.2.13

References

and 10 more references

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

CVE-2026-829739.4
Improper neutralization of CRLF sequences in IMAP command construction in…
CVE-2026-1007179.9
froxlor is a server administration panel. In versions 2.3.10 and earlier,…
CVE-2026-551598.8
luci-app-adblock-fast a WebUI for fast, lightweight DNS-based ad-blocker for OpenWrt…
CVE-2026-405308.0
An improper neutralization of CRLF sequences ('CRLF injection') vulnerability in User…
CVE-2026-850778.2
Sanic is an opensource python web server/framework. Prior to version 24.12.1, and in…
CVE-2026-909379.9
froxlor versions before 2.2.5 fail to validate newline characters in subdomain redirect…

Frequently asked

Is CVE-2026-42578 being actively exploited?

CVE-2026-42578 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 1.15%.

How severe is CVE-2026-42578?

CVE-2026-42578 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 1.15% probability of exploitation.

Which products are affected by CVE-2026-42578?

Affected products include Netty.

How do I fix CVE-2026-42578?

Upgrade affected software to a fixed version, for example Netty 4.2.13 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-42578 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

See how prioritisation worksBook a demo

Get Patch this first every Monday

Five vulnerabilities that matter this week, ranked on real exploitation. Plain language, one email, no spam.

You can unsubscribe with one click from every issue. We handle your details as described in our privacy policy.

Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.