Resource exhaustion in Io.netty Netty-Codec-Http3
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (39.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 39.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.000
Affected products
- Io.netty Netty-Codec-Http3 — versions >= 4.2.0.Alpha1, < 4.2.13.Final
- Netty — versions >= 4.2.0.Alpha1, < 4.2.13.Final
Weakness classification (CWE)
References
- github.com/netty/netty/security/advisories/GHSA-2c5c-chwr-9hqw (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-42582?
- CVE-2026-42582 is a high-severity vulnerability in Io.netty Netty-Codec-Http3, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-05-13.
- How severe is CVE-2026-42582?
- High severity. CVSS v3 base score is 7.5 out of 10.