# CVE-2026-45416: Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes > Attackers can cause memory exhaustion and denial of service by sending small TLS ClientHello packets that trigger large pre-allocations in Netty's SNI handler. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 12 Jun 2026 - **Updated:** 18 Sep 2026 - **Also known as:** CLEANSTART-2026-FY04918, CLEANSTART-2026-IR80784, CLEANSTART-2026-SE44846, CLEANSTART-2026-TV10241, CLEANSTART-2026-YI20813, DEBIAN-CVE-2026-45416, ECHO-35d4-0eba-523a, GHSA-x4gw-5cx5-pgmh, MINI-22v9-hj6c-qjmq, MINI-28f6-pj9c-c8x7, MINI-292c-r35f-qrrm, MINI-2f8h-hwxg-rwpj, MINI-2f8r-qcgq-xqw6, MINI-2gxm-37wr-789g, MINI-2m72-r465-4hvh, MINI-2mff-m8xx-xcgp, MINI-3287-4p8f-5v53, MINI-3942-cmcr-2w82, MINI-3f9v-7rj3-9gm5, MINI-3g5h-7h47-67f6, MINI-3g95-g257-p83c, MINI-3ggg-fj69-ppm8, MINI-3rvm-5vc8-qx3p, MINI-3v36-grr8-5jvw, MINI-3wpr-wr3p-ccfq, MINI-439q-vcpc-wj75, MINI-48fc-75rf-68pw, MINI-4c4q-mqhq-9jjv, MINI-4f3g-q5fm-pwf8, MINI-4gvh-fw3f-5x66, MINI-4p2m-p48x-hwrw, MINI-4p8p-mjr9-vjq9, MINI-4v2r-pj58-p56c, MINI-59g9-xh66-hv5q, MINI-5hm9-x79p-x79f, MINI-698f-qrfv-w58p, MINI-69w7-447w-2q3f, MINI-6j79-2j22-qv76, MINI-6ph9-jr92-922r, MINI-6q68-78h5-w6rj, MINI-6w8x-28p3-2cj5, MINI-6wwc-2j74-987w, MINI-73m3-33vp-xxx5, MINI-773g-5mgw-4hch, MINI-78r6-r9r5-55wg, MINI-7q7m-p5cc-wgxx, MINI-7rhq-j36v-mqpf, MINI-7whh-qcjj-5v4m, MINI-8g92-52fw-22qp, MINI-8jr2-f2gr-6pgp, MINI-8r7j-56vm-r42g, MINI-92wv-vr37-q4qv, MINI-96h8-x35v-87mj, MINI-9747-258c-c366, MINI-9844-9mrx-8gpx, MINI-9cpx-p6c4-jvvr, MINI-9fjx-h8pg-4j2c, MINI-9rgh-9hc6-58rc, MINI-9rm6-m86x-ccfr, MINI-c873-mphr-jmpp, MINI-c8j7-c5hw-c3jf, MINI-cgw8-7mjv-55w6, MINI-chmg-p5hw-4r2g, MINI-f38j-62p5-cfrg, MINI-f928-5qfp-p36r, MINI-f9qx-v86p-q9j7, MINI-fhvj-5pvx-9x6m, MINI-g4hp-pq7p-jpcg, MINI-g65m-pqwh-mwmm, MINI-g688-fc74-qxp3, MINI-g795-jmv6-6wg2, MINI-gg3j-5c22-mmwg, MINI-gjjx-vfhv-c88p, MINI-gmhj-54cv-45cf, MINI-grg9-mff3-wwq3, MINI-gww4-mp3w-9x23, MINI-h34r-6j24-vg5h, MINI-h72x-pr5c-vhrr, MINI-hfvp-mqr5-jmrq, MINI-hrjq-44rp-368f, MINI-hrmg-chh9-54mw, MINI-j9p2-wvpr-35r3, MINI-j9pq-45g5-9353, MINI-jrgc-v9j3-3pgg, MINI-jrhw-h62q-jj74, MINI-jvqf-pr46-w3qq, MINI-jwvq-hvcf-2vq8, MINI-jww2-p263-wjmf, MINI-mfp8-jw28-4pf5, MINI-mj54-cffr-cf8p, MINI-mm3w-qf64-75pc, MINI-mpp5-5983-75fh, MINI-mq3f-5pmh-rf54, MINI-p658-7cfv-3269, MINI-pgfr-p887-qg6j, MINI-pgq9-p4v3-cq67, MINI-pjcj-8vw2-wch6, MINI-pp6w-q65m-hm4v, MINI-pq26-9pwq-j9cq, MINI-pwm7-mh69-598q, MINI-q4hm-mc9v-8rhm, MINI-q94m-rr38-gvcv, MINI-qcr8-g3c4-57f7, MINI-qgp8-xw2q-f8cx, MINI-qm65-2m5g-45v4, MINI-qm6h-9mgp-hvf7, MINI-qw4h-7x49-83c6, MINI-qw4w-9mxp-f89w, MINI-r8h5-w8hq-vr97, MINI-rfwh-9g7p-frhj, MINI-rm52-qv9f-jpqh, MINI-rqj8-9w79-cmfr, MINI-rvff-2xgx-qxqv, MINI-rvjx-x3g3-6jcv, MINI-v5p6-8cvc-mw9j, MINI-v9wx-9r35-jx9r, MINI-vhgg-5vw4-4gw7, MINI-vqr8-c2p7-9453, MINI-vqvh-6cch-24v8, MINI-vr4g-fq9v-jj8v, MINI-w3rg-mcpm-m3vq, MINI-w455-xw8x-w2m3, MINI-w5m3-cw48-8gj9, MINI-wc44-29qx-v8vf, MINI-wgm9-jx2p-wf9v, MINI-wq9q-w4v5-fj4x, MINI-x2g5-rghp-q8fx, MINI-xcxr-8vhj-v9mc, MINI-xrj7-35q7-3pm8, MINI-xv6h-97vf-83f4, MINI-xww6-78p3-hgh3, MINI-xxj9-q5pj-g88f, ROOT-APP-MAVEN-CVE-2026-45416, UBUNTU-CVE-2026-45416 ## What is CVE-2026-45416? CVE-2026-45416 is a high-severity denial of service vulnerability in Netty Netty, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, SslClientHelloHandler.decode() reads the 24-bit TLS handshake length and, when the ClientHello does not fit in the first record, eagerly allocates `ctx.alloc().buffer(handshakeLength)` (line 161). The guard at line 140 is `handshakeLength > maxClientHelloLength && maxClientHelloLength != 0`, and the commonly-used SniHandler/AbstractSniHandler constructors (SniHandler(Mapping), SniHandler(AsyncMapping), AbstractSniHandler()) pass maxClientHelloLength=0 and handshakeTimeoutMillis=0, so the length guard is disabled and no timeout is scheduled. A 16 MiB request exceeds the default pooled chunk size and becomes a huge/unpooled allocation performed immediately. The buffer is retained in the handler until the channel closes. Versions 4.1.135.Final and 4.2.15.Final patch the issue. Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling) ## Which versions are affected by CVE-2026-45416? 4 open source packages ship an affected version, including io.netty:netty-handler. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `io.netty:netty-handler` | Maven | All versions | 4.1.135.Final | | `io.netty:netty-handler` | Maven | All versions | 4.1.135.Final | | `io.netty:netty-handler` | Maven | From 4.2.0.Final | 4.2.15.Final | | `io.netty:netty-handler` | Maven | From 4.2.0.Final | 4.2.15.Final | Products: Netty Netty. ## How do I fix CVE-2026-45416? Upgrade io.netty:netty-handler to a fixed version for your release line: 4.1.135.Final or 4.2.15.Final. ## Is CVE-2026-45416 being exploited? There is no known exploitation of CVE-2026-45416 in the wild and no public exploit code. ## 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-2026-45416 and fix it if it is affected. What it is: CVE-2026-45416 is a high-severity denial of service vulnerability in Netty Netty, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-45416 in the wild and no public exploit code. Affected packages and fixed versions: - io.netty:netty-handler (Maven): affected all versions; fixed in 4.1.135.Final - io.netty:netty-handler (Maven): affected all versions; fixed in 4.1.135.Final - io.netty:netty-handler (Maven): affected from 4.2.0.Final; fixed in 4.2.15.Final - io.netty:netty-handler (Maven): affected from 4.2.0.Final; fixed in 4.2.15.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-2026-45416/ (Markdown: https://insights.sbomify.com/CVE-2026-45416/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45416 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45416 - OSV: https://osv.dev/vulnerability/CVE-2026-45416 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-45416/ Summaries are generated and may contain mistakes; the official description above is the record.