Review reviewHigh

CVE-2026-42582

netty netty, netty-codec-http3

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.

CVSS: 7.5
EPSS: 0.44%
CISA KEV: Not listed
Published: 2026.05.14

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.44%

Technical severityCVSS 7.5

Vulnerability overview

Affected product and versions

Product: netty netty, netty-codec-http3
Affected versions: >= 4.2.0.Alpha1, < 4.2.13.Final, >= 4.2.0 < 4.2.13
Fixed versions: 4.2.13

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that netty netty, netty-codec-http3 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE: CWE-770, CWE-789