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CVE-2026-42583

Netty denial of service

7.5 HIGHPublic exploitEPSS 0.49%
  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, Lz4FrameDecoder allocates a ByteBuf of size decompressedLength (up to 32 MB per block) before LZ4 runs. A peer only needs a 21-byte header plus compressedLength payload bytes - 22 bytes if compressedLength == 1 - to force that allocation. 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
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Netty≥ 4.2.0 < 4.2.13 · < 4.1.133

Remediation

Fixed in
Netty≥ 4.2.13

References

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Frequently asked

Is CVE-2026-42583 being actively exploited?

CVE-2026-42583 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.49%.

How severe is CVE-2026-42583?

CVE-2026-42583 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.49% probability of exploitation.

Which products are affected by CVE-2026-42583?

Affected products include Netty.

How do I fix CVE-2026-42583?

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-2026-42583 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.

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