How severe is CVE-2026-42582?

CVE-2026-42582 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-2026-42582 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42582?

CVE-2026-42582 affects Netty. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-42582?

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-2026-42582 have an EU (EUVD) identifier?

Yes. CVE-2026-42582 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30125.

When was CVE-2026-42582 published?

CVE-2026-42582 was published on 2026-05-13 and last updated on 2026-06-17.

CVE-2026-42582

CVE-2026-42582 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-770.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (35th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30125
Weakness: CWE-770
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, when decoding header blocks, the non-Huffman branch of io.netty.handler.codec.http3.QpackDecoder#decodeHuffmanEncodedLiteral may execute new byte[length] for a string literal before verifying that length bytes are actually present in the compressed field section. The wire encoding allows a very large length to be expressed in few bytes. There is no check that length <= in.readableBytes() before new byte[length]. This vulnerability is fixed in 4.2.13.Final.

Frequently asked questions

What is CVE-2026-42582?: Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final, when decoding header blocks, the non-Huffman branch of io.netty.handler.codec.http3.QpackDecoder#decodeHuffmanEncodedLiteral may execute new byte[length] for a string literal before verifying that length bytes are actually present in the compressed field section. The wire encoding allows a very large length to be expressed in few bytes. There is no check that length <= in.readableBytes() before new byte[length]. This vulnerability is fixed in 4.2.13.Final.
How severe is CVE-2026-42582?: CVE-2026-42582 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-2026-42582 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42582?: CVE-2026-42582 affects Netty. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-42582?: 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-2026-42582 have an EU (EUVD) identifier?: Yes. CVE-2026-42582 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30125.
When was CVE-2026-42582 published?: CVE-2026-42582 was published on 2026-05-13 and last updated on 2026-06-17.

References

https://github.com/netty/netty/security/advisories/GHSA-2c5c-chwr-9hqw

Affected products (1)

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

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