{"id":"CVE-2026-47244","aliases":["GHSA-5x3r-wrvg-rp6q"],"url":"https://o3.security/vulnerability/CVE-2026-47244","summary":"Netty HTTP/2: Advertised MAX_CONCURRENT_STREAMS are not enforced","details":"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.","published":"2026-06-12T14:23:50.316Z","modified":"2026-08-12T03:51:48.224280522Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":{"score":0.00292,"percentile":0.21306,"asOf":"2026-09-02"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Maven","name":"io.netty:netty-codec-http2","fixedVersion":"4.2.15.Final"},{"ecosystem":"Maven","name":"io.netty:netty-codec-http2","fixedVersion":"4.1.135.Final"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/netty/netty/releases/tag/netty-4.1.135.Final"},{"type":"WEB","url":"https://github.com/netty/netty/releases/tag/netty-4.2.15.Final"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47244.json"},{"type":"ADVISORY","url":"https://github.com/netty/netty/security/advisories/GHSA-5x3r-wrvg-rp6q"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47244"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:48.224280522Z"}}