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CVE-2026-55831

Netty denial of service

7.5 HIGHPublic exploitEPSS 0.66%
  1. Published20 Jul 2026

Description

Netty is a network application framework for development of protocol servers and clients. Prior to 4.1.136.Final and 4.2.16.Final, Netty's SPDY SETTINGS decoder accepts a peer-declared SETTINGS entry count up to the 24-bit frame-length limit and materializes every unique setting ID in `DefaultSpdySettingsFrame`, allowing a remote SPDY/3.1 peer to send a syntactically valid roughly 2 MiB SETTINGS frame that creates 262144 map entries and amplifies network input into heap growth and ordered-map insertion work. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

CVSS 3.1 breakdown

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

Affected products

Netty≥ 4.1.0 < 4.1.136 · ≥ 4.2.0 < 4.2.16

Remediation

Fixed in
Netty≥ 4.1.136

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Frequently asked

Is CVE-2026-55831 being actively exploited?

CVE-2026-55831 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.66%.

How severe is CVE-2026-55831?

CVE-2026-55831 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.66% probability of exploitation.

Which products are affected by CVE-2026-55831?

Affected products include Netty.

How do I fix CVE-2026-55831?

Upgrade affected software to a fixed version, for example Netty 4.1.136 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-55831 against the real software inventory on every managed device, as each hourly inventory arrives. 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.

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