# CVE-2026-42579: Netty: DNS Codec Input Validation Bypass in Netty (Encoder + Decoder) - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`) - **Exploited in the wild:** Not known - **Fix available:** Yes - **Published:** 13 May 2026 - **Updated:** 18 Sep 2026 - **Also known as:** CLEANSTART-2026-IT89059, CLEANSTART-2026-OV40735, CLEANSTART-2026-RJ93794, CLEANSTART-2026-VE23252, CLSA-2026-1780361386, CLSA-2026-1793138621, DEBIAN-CVE-2026-42579, ECHO-d753-ce86-8248, GHSA-cm33-6792-r9fm, MINI-284j-mj52-6p2p, MINI-2h9x-5qf5-jm6h, MINI-2r7f-vrg3-w5g8, MINI-2wqj-83h2-84px, MINI-34fc-q7vp-8wpr, MINI-38f5-ph4p-mrg6, MINI-49rc-v66v-qwmh, MINI-4q76-fwm4-r7rf, MINI-55gx-gq34-7xpm, MINI-586p-j7q9-w5wx, MINI-58gx-v48w-hhx9, MINI-5g2c-q8x7-hr4f, MINI-5gq2-fr3h-g8f4, MINI-6797-rfjc-7fh6, MINI-69p2-jhv5-j978, MINI-6c7v-g664-2g8f, MINI-6j93-c2pq-p899, MINI-6jj3-4gmg-xrmj, MINI-6w44-fv3f-hqv2, MINI-84pg-7vx9-x3v7, MINI-84q7-q73v-6vf5, MINI-8fc7-w3hj-r8f2, MINI-8gmf-jm84-pj3m, MINI-9754-2x4w-75fm, MINI-9cfv-w93p-m593, MINI-9jhx-g7mr-77qp, MINI-9m4w-phx7-j8px, MINI-cf7p-j8jw-vcc8, MINI-cx5v-5hr6-4qh4, MINI-f8g6-342x-w23g, MINI-ffh9-p4w4-3w6r, MINI-fp79-4fc5-f6wf, MINI-fqf2-hq4q-34mr, MINI-fxrf-8jwx-5w94, MINI-ggrv-gr2c-h797, MINI-gj2c-vc4r-2fg6, MINI-grgc-xxrf-25cf, MINI-h9x9-526r-2pc8, MINI-j7r2-wx9m-9g4c, MINI-jc4j-7582-qqwf, MINI-jfwr-7f63-wvfh, MINI-jj4f-f555-5rj4, MINI-m5m4-hhr7-2h2q, MINI-mfcq-x4rh-6rjw, MINI-mpcm-mqc5-5hgh, MINI-mr42-xm4f-5p88, MINI-pcv4-7cwf-8hwx, MINI-pfwg-5c3w-xcgg, MINI-ph9p-r4v7-7hg5, MINI-pv4w-qm8h-p7f4, MINI-qh78-rmpp-rrh6, MINI-qm36-6vm5-qw59, MINI-qq4x-8mrf-qp5q, MINI-qqcv-wq34-62fq, MINI-r39p-wv84-j7p3, MINI-rc9c-hfxw-vfvv, MINI-rf7w-7g58-5g26, MINI-rfjr-g9c9-5xhv, MINI-rgcg-gxj7-q5qv, MINI-rh5f-fjm2-c5p3, MINI-rhrm-59g2-jr6x, MINI-rmg9-4r68-588r, MINI-v3c4-9rjv-cvcv, MINI-v46g-58m3-3xf3, MINI-v4qp-5jjr-3x8m, MINI-vvvg-w6vf-j5mj, MINI-w5mm-8rc9-jprf, MINI-x6f4-475h-x9rj, MINI-x878-pgp3-vvh5, MINI-xg4f-f9x5-mfv2, RHLW-2026-02416b185203289c, ROOT-APP-MAVEN-CVE-2026-42579, UBUNTU-CVE-2026-42579 ## What is CVE-2026-42579? CVE-2026-42579 is a high-severity vulnerability in Netty Netty, published on 13 May 2026. ### Official description Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Netty's DNS codec does not enforce RFC 1035 domain name constraints during either encoding or decoding. This creates a bidirectional attack surface: malicious DNS responses can exploit the decoder, and user-influenced hostnames can exploit the encoder. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final. Weakness: CWE-1286 (Improper Validation of Syntactic Correctness of Input), CWE-626 (Null Byte Interaction Error (Poison Null Byte)), CWE-400 (Uncontrolled Resource Consumption), CWE-20 (Improper Input Validation) ## Which versions are affected by CVE-2026-42579? 4 open source packages ship an affected version, including io.netty:netty-codec-dns. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `io.netty:netty-codec-dns` | Maven | All versions | 4.1.133.Final | | `io.netty:netty-codec-dns` | Maven | All versions | 4.1.133.Final | | `io.netty:netty-codec-dns` | Maven | From 4.2.0.Alpha1 | 4.2.13.Final | | `io.netty:netty-codec-dns` | Maven | From 4.2.0.Alpha1 | 4.2.13.Final | Products: Netty Netty. ## How do I fix CVE-2026-42579? Upgrade io.netty:netty-codec-dns to a fixed version for your release line: 4.1.133.Final or 4.2.13.Final. ## Is CVE-2026-42579 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42579 exists. ## Other vulnerabilities in Netty Netty - [CVE-2026-75595](https://insights.sbomify.com/CVE-2026-75595/): Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext (critical 9.1) - [CVE-2026-75596](https://insights.sbomify.com/CVE-2026-75596/): Netty: Fragmented ClientHello records trigger quadratic pre-handshake reassembly in default SNI parsing (high 8.7) - [CVE-2026-59901](https://insights.sbomify.com/CVE-2026-59901/): Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang (high 8.7) - [CVE-2026-55851](https://insights.sbomify.com/CVE-2026-55851/): Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion (high 8.7) - [CVE-2026-56745](https://insights.sbomify.com/CVE-2026-56745/): Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion (high 8.7) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-42579 and fix it if it is affected. What it is: CVE-2026-42579 is a high-severity vulnerability in Netty Netty, published on 13 May 2026. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42579 exists. Affected packages and fixed versions: - io.netty:netty-codec-dns (Maven): affected all versions; fixed in 4.1.133.Final - io.netty:netty-codec-dns (Maven): affected all versions; fixed in 4.1.133.Final - io.netty:netty-codec-dns (Maven): affected from 4.2.0.Alpha1; fixed in 4.2.13.Final - io.netty:netty-codec-dns (Maven): affected from 4.2.0.Alpha1; fixed in 4.2.13.Final Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-42579/ (Markdown: https://insights.sbomify.com/CVE-2026-42579/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42579 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42579 - OSV: https://osv.dev/vulnerability/CVE-2026-42579 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-42579/ Summaries are generated and may contain mistakes; the official description above is the record.