{"cve":"CVE-2021-21409","nvd":{"published":"2021-03-30T15:15:14.573","modified":"2026-10-08T22:17:06.500","status":"Modified","description":"Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. In Netty (io.netty:netty-codec-http2) before version 4.1.61.Final there is a vulnerability that enables request smuggling. The content-length header is not correctly validated if the request only uses a single Http2HeaderFrame with the endStream set to to true. This could lead to request smuggling if the request is proxied to a remote peer and translated to HTTP/1.1. This is a followup of GHSA-wm47-8v5p-wjpj/CVE-2021-21295 which did miss to fix this one case. This was fixed as part of 4.1.61.Final.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","score":5.9},"cwes":["CWE-444"],"references":["https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21295","https://github.com/netty/netty/commit/b0fa4d5aab4215f3c22ce6123dd8dd5f38dc0432","https://github.com/netty/netty/security/advisories/GHSA-f256-j965-7f32","https://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj","https://lists.apache.org/thread.html/r0b09f3e31e004fe583f677f7afa46bd30110904576c13c5ac818ac2c%40%3Cissues.flink.apache.org%3E"],"products":["debian:debian_linux","netapp:oncommand_api_services","netapp:oncommand_workflow_automation","netty:netty","oracle:banking_corporate_lending_process_management","oracle:banking_credit_facilities_process_management","oracle:banking_trade_finance_process_management","oracle:coherence","oracle:communications_brm_-_elastic_charging_engine","oracle:communications_cloud_native_core_console","oracle:communications_cloud_native_core_policy","oracle:communications_design_studio","oracle:communications_messaging_server","oracle:helidon","oracle:jd_edwards_enterpriseone_tools","oracle:nosql_database","oracle:primavera_gateway","quarkus:quarkus"],"source":"nvd","synced_at":"2026-10-19T21:17:01.373894544+00:00"},"epss":{"cve":"CVE-2021-21409","score":0.04935,"percentile":0.92081,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-f256-j965-7f32","url":"https://osv.dev/vulnerability/GHSA-f256-j965-7f32","summary":"Possible request smuggling in HTTP/2 due missing validation of content-length","modified":"2026-09-10T03:49:02.310119365Z","packages":[{"ecosystem":"Maven","name":"io.netty:netty-codec-http2","purl":"pkg:maven/io.netty/netty-codec-http2","ranges":[">=4.0.0 <4.1.61.Final"],"fixed":["4.1.61.Final"]},{"ecosystem":"Maven","name":"org.jboss.netty:netty","purl":"pkg:maven/org.jboss.netty/netty","ranges":["all versions"],"fixed":[]},{"ecosystem":"Maven","name":"io.netty:netty","purl":"pkg:maven/io.netty/netty","ranges":["all versions"],"fixed":[]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}