{"id":"UBUNTU-CVE-2026-123611","details":"rustls before 0.23.46 contains a key exchange downgrade vulnerability that allows network attackers to poison the per-server-name key-exchange group record via an unauthenticated ServerHello. Attackers can answer one connection with a ServerHello selecting X25519, causing later ClientHellos to send only classical shares and lose post-quantum confidentiality.","modified":"2026-11-10T02:50:22.487540384Z","published":"2026-11-09T00:00:00Z","upstream":["CVE-2026-123611"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-123611"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-123611"},{"type":"REPORT","url":"https://rustsec.org/advisories/RUSTSEC-2026-0349.html"},{"type":"REPORT","url":"https://github.com/advisories/GHSA-w44r-93j7-qv28"},{"type":"REPORT","url":"https://github.com/rustls/rustls/pull/3355"},{"type":"REPORT","url":"https://github.com/rustls/rustls/security/advisories/GHSA-w44r-93j7-qv28"},{"type":"REPORT","url":"https://www.vulncheck.com/advisories/rustls-before-0.23.46-key-exchange-downgrade-via-unauthenticated-serverhello"}],"affected":[{"package":{"name":"rust-rustls","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/rust-rustls?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.21.6-3","0.21.7-1","0.21.9-1","0.21.10-1"],"ecosystem_specific":{"binaries":[{"binary_version":"0.21.10-1","binary_name":"librust-rustls-dev"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-123611.json"}},{"package":{"name":"rust-rustls","ecosystem":"Ubuntu:26.10","purl":"pkg:deb/ubuntu/rust-rustls?arch=source&distro=stonking"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.23.36+ds-1","0.23.41+ds-1"],"ecosystem_specific":{"binaries":[{"binary_version":"0.23.41+ds-1","binary_name":"librust-rustls-dev"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-123611.json"}},{"package":{"name":"rust-rustls","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/rust-rustls?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.23.26+ds-1","0.23.33+ds-3build2","0.23.35+ds-1","0.23.35+ds-1build1","0.23.36+ds-1"],"ecosystem_specific":{"binaries":[{"binary_name":"librust-rustls-dev","binary_version":"0.23.36+ds-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-123611.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"},{"type":"Ubuntu","score":"medium"}]}