# CVE-2026-47244: Netty HTTP/2: Advertised MAX_CONCURRENT_STREAMS are not enforced > Netty HTTP/2 servers fail to enforce concurrent stream limits by default, allowing attackers to exhaust resources via excessive streams, causing denial of service. - **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`) - **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:** 12 Jun 2026 - **Also known as:** CLEANSTART-2026-AK01289, CLEANSTART-2026-DP99437, CLEANSTART-2026-SI32200, CLEANSTART-2026-VE14667, CLEANSTART-2026-XH56428, CLSA-2026-1792694876, DEBIAN-CVE-2026-47244, ECHO-c5b5-54e8-9e68, GHSA-5x3r-wrvg-rp6q, MINI-26wr-38hq-xv9h, MINI-277j-g2vr-6w4r, MINI-29qh-x863-vh35, MINI-2f8x-wr3w-4c73, MINI-2hc8-pv42-r2v9, MINI-2prh-7g95-j4g5, MINI-3675-9vm8-p958, MINI-3vw5-672f-4f6m, MINI-3xqr-9xv2-7x24, MINI-3xx7-52c7-5fj4, MINI-449w-fq9g-c98q, MINI-44c9-gfrc-rg77, MINI-4fwq-p863-9f9q, MINI-4gpq-62q5-cq7j, MINI-4v36-qjw9-wxx3, MINI-54h8-rwvr-q2h2, MINI-5jg9-grxq-q3x4, MINI-5xqh-9g67-fh69, MINI-6qfx-77jc-86h4, MINI-7mcm-8w3p-gw98, MINI-8rmj-gmjx-fmx3, MINI-94rh-46mw-q78h, MINI-97gw-wx9m-f8vf, MINI-9887-j495-67wq, MINI-9987-4ccg-hccr, MINI-9pr7-w7fr-3rq5, MINI-c753-f844-hr6p, MINI-c98g-8fmx-hqhm, MINI-cfrc-9g96-4962, MINI-ch4p-j36q-ppm7, MINI-cp3w-r6cf-2365, MINI-cwjq-83vx-c55g, MINI-f8w4-88wh-86pf, MINI-fcf7-hrvm-49c9, MINI-ffgh-hv93-gp2p, MINI-fhxc-fvhq-48pv, MINI-g254-7hc7-jc6p, MINI-g8hm-2jhg-q4fq, MINI-g93w-h236-32mp, MINI-g99p-xpc7-683g, MINI-g9mr-89g4-fj6g, MINI-gh47-826q-xmh6, MINI-gjv3-5vph-5qm3, MINI-grf5-32pq-6cqw, MINI-h6mx-c5vp-v32x, MINI-hx28-82r8-fcwq, MINI-j2w8-842q-2mmj, MINI-jc4j-g9xr-hf94, MINI-jchh-845m-gvr7, MINI-m5pj-gwqq-vc54, MINI-m94x-vjm7-wgjx, MINI-mfxq-6fpj-7gh7, MINI-mj88-vxcv-rh34, MINI-p355-w7cv-v8j5, MINI-p5wh-625r-8w8w, MINI-p7jc-pcf2-mgfj, MINI-pcjr-6qgg-5cg8, MINI-pqwp-vf92-hp44, MINI-pv39-6337-xq59, MINI-q377-8chv-jw9c, MINI-q5cw-2p76-gw65, MINI-qmm7-ch9h-m8hp, MINI-qqq4-pq3v-mx3f, MINI-rjhq-wqcr-5rcg, MINI-rmvx-ch69-579g, MINI-rvm6-g4v9-23cr, MINI-vcx3-45v4-wrgf, MINI-vv93-f4fh-jww9, MINI-w5jj-j7pw-g382, MINI-w7xq-98p6-7gm7, MINI-w92g-4gr5-pp89, MINI-wqc9-4f27-3r87, MINI-wwpf-jrhx-3x6q, MINI-x75f-6qcj-g6w6, MINI-x7cf-5hqc-g98g, MINI-x955-gf78-8425, MINI-xvc7-cpx5-rw2q, MINI-xx27-rr4m-q72f, ROOT-APP-MAVEN-CVE-2026-47244, UBUNTU-CVE-2026-47244 ## What is CVE-2026-47244? CVE-2026-47244 is a medium-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, DefaultHttp2Connection.DefaultEndpoint initialises maxActiveStreams/maxStreams to Integer.MAX_VALUE, and Http2Settings never inserts SETTINGS_MAX_CONCURRENT_STREAMS by default (Http2Settings.java:305-307 only clamps a user-supplied value). Unless the application explicitly calls initialSettings().maxConcurrentStreams(n), a Netty HTTP/2 server advertises no limit and enforces none locally. Each open stream allocates a DefaultStream object, PropertyMap slots, flow-controller state and IntObjectHashMap entry; with ~2^30 permissible odd stream IDs a single TCP connection can create hundreds of thousands of long-lived stream objects. This is also the precondition for CVE-2023-44487-style Rapid-Reset amplification, where the absence of a low concurrent cap multiplies backend work. Versions 4.1.135.Final and 4.2.15.Final patch the issue. Weakness: CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2026-47244? 4 open source packages ship an affected version, including io.netty:netty-codec-http2. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `io.netty:netty-codec-http2` | Maven | All versions | 4.1.135.Final | | `io.netty:netty-codec-http2` | Maven | All versions | 4.1.135.Final | | `io.netty:netty-codec-http2` | Maven | From 4.2.0.Final | 4.2.15.Final | | `io.netty:netty-codec-http2` | Maven | From 4.2.0.Final | 4.2.15.Final | Products: Netty Netty. ## How do I fix CVE-2026-47244? Upgrade io.netty:netty-codec-http2 to a fixed version for your release line: 4.1.135.Final or 4.2.15.Final. ## Is CVE-2026-47244 being exploited? There is no known exploitation of CVE-2026-47244 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-2026-47244 and fix it if it is affected. What it is: CVE-2026-47244 is a medium-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-2026-47244 in the wild and no public exploit code. Affected packages and fixed versions: - io.netty:netty-codec-http2 (Maven): affected all versions; fixed in 4.1.135.Final - io.netty:netty-codec-http2 (Maven): affected all versions; fixed in 4.1.135.Final - io.netty:netty-codec-http2 (Maven): affected from 4.2.0.Final; fixed in 4.2.15.Final - io.netty:netty-codec-http2 (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-2026-47244/ (Markdown: https://insights.sbomify.com/CVE-2026-47244/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47244 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47244 - OSV: https://osv.dev/vulnerability/CVE-2026-47244 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-47244/ Summaries are generated and may contain mistakes; the official description above is the record.