{"document":{"category":"csaf_vex","csaf_version":"2.0","title":"CVE-2026-45416: Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes","publisher":{"category":"vendor","name":"HarborGuard Database","namespace":"https://database.harborguard.co"},"tracking":{"id":"CVE-2026-45416","status":"final","version":"1","initial_release_date":"2026-06-12T14:10:05.585Z","current_release_date":"2026-06-12T15:07:07.365Z","revision_history":[{"date":"2026-06-12T14:10:05.585Z","number":"1","summary":"Initial machine-readable export from HarborGuard."}]},"distribution":{"tlp":{"label":"WHITE"},"text":"Public CVE data; freely redistributable."},"notes":[{"category":"description","text":"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, SslClientHelloHandler.decode() reads the 24-bit TLS handshake length and, when the ClientHello does not fit in the first record, eagerly allocates `ctx.alloc().buffer(handshakeLength)` (line 161). The guard at line 140 is `handshakeLength > maxClientHelloLength && maxClientHelloLength != 0`, and the commonly-used SniHandler/AbstractSniHandler constructors (SniHandler(Mapping), SniHandler(AsyncMapping), AbstractSniHandler()) pass maxClientHelloLength=0 and handshakeTimeoutMillis=0, so the length guard is disabled and no timeout is scheduled. A 16 MiB request exceeds the default pooled chunk size and becomes a huge/unpooled allocation performed immediately. The buffer is retained in the handler until the channel closes. Versions 4.1.135.Final and 4.2.15.Final patch the issue.","title":"CVE description"}],"references":[{"category":"self","summary":"CVE-2026-45416 on HarborGuard Database","url":"https://database.harborguard.co/cve/CVE-2026-45416"},{"category":"external","summary":"CVE Record","url":"https://www.cve.org/CVERecord?id=CVE-2026-45416"},{"category":"external","summary":"https://github.com/netty/netty/security/advisories/GHSA-x4gw-5cx5-pgmh","url":"https://github.com/netty/netty/security/advisories/GHSA-x4gw-5cx5-pgmh"},{"category":"external","summary":"https://github.com/netty/netty/releases/tag/netty-4.1.135.Final","url":"https://github.com/netty/netty/releases/tag/netty-4.1.135.Final"},{"category":"external","summary":"https://github.com/netty/netty/releases/tag/netty-4.2.15.Final","url":"https://github.com/netty/netty/releases/tag/netty-4.2.15.Final"}]},"product_tree":{"branches":[{"category":"vendor","name":"netty","branches":[{"category":"product_name","name":"netty","branches":[{"category":"product_version","name":">= 4.2.0.Final, < 4.2.15.Final","product":{"name":"netty netty >= 4.2.0.Final, < 4.2.15.Final","product_id":"CSAFPID-1","product_identification_helper":{"cpe":"cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"< 4.1.135.Final","product":{"name":"netty netty < 4.1.135.Final","product_id":"CSAFPID-2","product_identification_helper":{"cpe":"cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*"}}}]}]}]},"vulnerabilities":[{"cve":"CVE-2026-45416","title":"Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes","notes":[{"category":"description","text":"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, SslClientHelloHandler.decode() reads the 24-bit TLS handshake length and, when the ClientHello does not fit in the first record, eagerly allocates `ctx.alloc().buffer(handshakeLength)` (line 161). The guard at line 140 is `handshakeLength > maxClientHelloLength && maxClientHelloLength != 0`, and the commonly-used SniHandler/AbstractSniHandler constructors (SniHandler(Mapping), SniHandler(AsyncMapping), AbstractSniHandler()) pass maxClientHelloLength=0 and handshakeTimeoutMillis=0, so the length guard is disabled and no timeout is scheduled. A 16 MiB request exceeds the default pooled chunk size and becomes a huge/unpooled allocation performed immediately. The buffer is retained in the handler until the channel closes. Versions 4.1.135.Final and 4.2.15.Final patch the issue.","title":"CVE description"}],"product_status":{"known_affected":["CSAFPID-1","CSAFPID-2"]},"scores":[{"cvss_v3":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"products":["CSAFPID-1","CSAFPID-2"]}],"remediations":[{"category":"none_available","details":"No fixed version is published yet. Monitor the upstream advisory.","product_ids":["CSAFPID-1","CSAFPID-2"]}]}]}