CVE-2026-42577

Q: How do I fix CVE-2026-42577?

Upgrade netty to 4.2.13 or later.

Q: Is CVE-2026-42577 being actively exploited?

Not that we know of. CVE-2026-42577 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.41% is the estimated probability that it will be exploited in the next 30 days. That is higher than 34% of all scored CVEs.

Q: How severe is CVE-2026-42577?

CVE-2026-42577 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2026-42577 affect?

Published advisories record a fix for netty (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

HIGH

7.5

CVSS v3

NVD

Description

Netty is an asynchronous, event-driven network application framework. From 4.2.0.Final to 4.2.13.Final , Netty's epoll transport fails to detect and close TCP connections that receive a RST after being half-closed, leading to stale channels that are never cleaned up and, in some code paths, a 100% CPU busy-loop in the event loop thread. This vulnerability is fixed in 4.2.13.Final.

CWE-772

How to fix

Remediation Available

nettyNVD

Affected:>= 4.2.0, < 4.2.13Fixed in:4.2.13CVE-2026-42577derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

0.41%probability of exploitation in 30 days

34thpercentile

Low risk: more likely to be exploited than 34% of all known CVEs.

References

Patch2

Vendor Advisory1

github.com

Related Vulnerabilities

Other CWE-772 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2003-0132	Medium	5.0	87%	-	Fix
CVE-2017-14495	High	7.5	84%	-	Fix
CVE-2021-22883	High	7.5	74%	-	Fix
CVE-2024-2398	High	8.6	36%	-	Fix
CVE-2020-9375	High	7.5	27%	-	-
CVE-1999-1127	High	7.5	18%	-	-

Common questions

How do I fix CVE-2026-42577?

Upgrade netty to 4.2.13 or later.

Is CVE-2026-42577 being actively exploited?

Not that we know of. CVE-2026-42577 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.41% is the estimated probability that it will be exploited in the next 30 days. That is higher than 34% of all scored CVEs.

How severe is CVE-2026-42577?

CVE-2026-42577 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-42577 affect?

Published advisories record a fix for netty (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-18.