{"cve":"CVE-2026-75595","nvd":{"published":"2026-08-19T21:17:37.563","modified":"2026-10-26T10:10:00.140","status":"Analyzed","description":"Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Fina and 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode checks the wrong offset before reading the four-byte TLS handshake header, so a ClientHello whose handshake header spans records can cause an IndexOutOfBoundsException and invoke select(ctx, null). This selects the default SslContext instead of the SNI-specific context. In deployments where per-SNI clientAuth=REQUIRE is the sole mutual TLS gate, the default SslContext uses clientAuth=NONE or clientAuth=OPTIONAL, and no application-layer certificate verification exists, an unauthenticated remote attacker can bypass the protected route's mutual TLS requirement. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","score":9.1},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","score":9.1},"cwes":["CWE-754"],"references":["https://github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7","https://github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139a0d7961","https://github.com/netty/netty/pull/17213","https://github.com/netty/netty/pull/17217","https://github.com/netty/netty/releases/tag/netty-4.1.137.Final"],"products":["netty:netty"],"source":"nvd","synced_at":"2026-10-26T10:28:23.151169805+00:00"},"epss":{"cve":"CVE-2026-75595","score":0.00316,"percentile":0.24246,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-c4c3-7fpv-j4q5","url":"https://osv.dev/vulnerability/GHSA-c4c3-7fpv-j4q5","summary":"Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext","modified":"2026-09-08T18:27:48.571082951Z","packages":[{"ecosystem":"Maven","name":"io.netty:netty-handler","purl":"pkg:maven/io.netty/netty-handler","ranges":[">=4.2.0.Final <4.2.17.Final"],"fixed":["4.2.17.Final"]},{"ecosystem":"Maven","name":"io.netty:netty-handler","purl":"pkg:maven/io.netty/netty-handler","ranges":["<4.1.137.Final"],"fixed":["4.1.137.Final"]}]}],"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."]}