{"action":"Upgrade stunnel4 to 3:5.56+dfsg-8 or later.","affected":[{"fixed":"3:5.56+dfsg-8","introduced":"0"}],"component":"stunnel4","cve_ids":[],"ecosystem":"Debian","ecosystem_qualifier":"Debian:12","exploited":false,"fixed_versions":["3:5.56+dfsg-8"],"id":"tcs_01M5NFAZEBJ680P46WS95PS0SS","modified_at":"2026-10-23T18:03:10.231626521Z","published_at":"2021-02-23T17:15:13.753Z","references":["https://osv.dev/vulnerability/DEBIAN-CVE-2021-20230","https://security-tracker.debian.org/tracker/CVE-2021-20230"],"severity":{"label":"high","score":7.5},"sources":[{"source":"osv","source_id":"DEBIAN-CVE-2021-20230","url":"https://osv.dev/vulnerability/DEBIAN-CVE-2021-20230"}],"summary":"A flaw was found in stunnel before 5.57, where it improperly validates client certificates when it is configured to use both redirect and verifyChain options. This flaw allows an attacker with a certi"}