How severe is CVE-2026-42583?

CVE-2026-42583 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-42583 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42583?

CVE-2026-42583 affects Netty. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-42583?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-42583 have an EU (EUVD) identifier?

Yes. CVE-2026-42583 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30126.

When was CVE-2026-42583 published?

CVE-2026-42583 was published on 2026-05-13 and last updated on 2026-06-17.

CVE-2026-42583

CVE-2026-42583 is a high-severity vulnerability in Netty with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (34th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30126
Weakness: CWE-400
Affected product: Netty
Published: 2026-05-13
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-42583?: 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.
How severe is CVE-2026-42583?: CVE-2026-42583 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-42583 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42583?: CVE-2026-42583 affects Netty. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-42583?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-42583 have an EU (EUVD) identifier?: Yes. CVE-2026-42583 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30126.
When was CVE-2026-42583 published?: CVE-2026-42583 was published on 2026-05-13 and last updated on 2026-06-17.

References

https://github.com/netty/netty/security/advisories/GHSA-mj4r-2hfc-f8p6

Affected products (1)

cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*

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