# CVE-2026-42577: Netty: epoll transport denial of service via RST on half-closed TCP connection > Attackers can cause a denial of service via CPU exhaustion in Netty's epoll transport by sending RST packets on half-closed connections. - **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:** 13 May 2026 - **Updated:** 14 May 2026 - **Also known as:** CLEANSTART-2026-KC30264, CLEANSTART-2026-RE04258, CLEANSTART-2026-RX83323, CLSA-2026-1793142374, DEBIAN-CVE-2026-42577, ECHO-ce1f-ec45-9a4d, GHSA-rwm7-x88c-3g2p, MINI-283c-9449-h98r, MINI-33g3-8mrm-qv2r, MINI-33vv-85cq-mv6j, MINI-353c-93p2-99jh, MINI-3g49-wcvh-725p, MINI-3h5c-qqqc-fmvx, MINI-48rg-46g3-76fm, MINI-4p97-3222-h8p2, MINI-5mf7-jq84-4rw7, MINI-5p2r-6gjw-j3gx, MINI-66w4-gw3v-q2pg, MINI-6gh2-xxf8-px9g, MINI-747v-jxq7-6q85, MINI-78mv-pp5h-r825, MINI-78r5-hr5q-jr88, MINI-78r5-qj83-qf7v, MINI-7fx3-8mmh-jj6v, MINI-87f2-f4hq-c82w, MINI-8qr5-3g78-7mfw, MINI-8rgv-563j-5rpg, MINI-8xjr-q9x7-gx95, MINI-986g-5cxv-pw3f, MINI-9jv5-27x8-685f, MINI-9wmg-jpmj-954m, MINI-cj8w-q8pq-mwpf, MINI-crrj-3hqc-q745, MINI-f2pw-wf3g-85qg, MINI-fp66-v8mh-vg72, MINI-fqw3-cvff-q92h, MINI-g36x-mq82-6385, MINI-g5gf-7wcj-xgxf, MINI-gg63-v82p-jxw9, MINI-grx8-g4mm-xrpj, MINI-h5fj-rhrf-c5g4, MINI-j5wh-9qxm-5r2x, MINI-m63r-hmhq-q78q, MINI-mpfg-j763-fxjr, MINI-q24w-m9f3-7rr8, MINI-q38x-jw75-f95j, MINI-q53p-qh3g-79w7, MINI-q6xx-m23m-74hw, MINI-qxx3-x6g5-rgw2, MINI-rfr9-mrg7-39p4, MINI-rvp3-fpfh-m6mc, MINI-v624-pf69-2pmj, MINI-w3g8-3w99-gfjh, MINI-w42x-mqxr-wfx4, MINI-w473-3vp6-3rvp, MINI-w5x8-3w3v-v798, MINI-w9pg-45qg-2c93, MINI-wwq6-ww22-hfhx, MINI-xqwr-4p2c-wr9f, ROOT-APP-MAVEN-CVE-2026-42577 ## What is CVE-2026-42577? CVE-2026-42577 is a high-severity denial of service vulnerability in Netty Netty, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Netty is an asynchronous, event-driven network application framework. From 4.2.0.Final to 4.2.13.Final , Netty's epoll transport fails to detect and close TCP connections that receive a RST after being half-closed, leading to stale channels that are never cleaned up and, in some code paths, a 100% CPU busy-loop in the event loop thread. This vulnerability is fixed in 4.2.13.Final. Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime) ## Which versions are affected by CVE-2026-42577? 2 open source packages ship an affected version, including io.netty:netty-transport-classes-epoll. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `io.netty:netty-transport-classes-epoll` | Maven | From 4.2.0.Final | 4.2.13.Final | | `io.netty:netty-transport-classes-epoll` | Maven | From 4.2.0.Final | 4.2.13.Final | Products: Netty Netty. ## How do I fix CVE-2026-42577? Upgrade io.netty:netty-transport-classes-epoll to 4.2.13.Final or later. ## Is CVE-2026-42577 being exploited? There is no known exploitation of CVE-2026-42577 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-2026-42577 and fix it if it is affected. What it is: CVE-2026-42577 is a high-severity denial of service vulnerability in Netty Netty, published on 13 May 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-2026-42577 in the wild and no public exploit code. Affected packages and fixed versions: - io.netty:netty-transport-classes-epoll (Maven): affected from 4.2.0.Final; fixed in 4.2.13.Final - io.netty:netty-transport-classes-epoll (Maven): affected from 4.2.0.Final; 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-2026-42577/ (Markdown: https://insights.sbomify.com/CVE-2026-42577/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42577 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42577 - OSV: https://osv.dev/vulnerability/CVE-2026-42577 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-42577/ Summaries are generated and may contain mistakes; the official description above is the record.