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 certificate signed by a Certificate Authority, which is not the one accepted by the stunnel server, to access the tunneled service instead of being redirected to the address specified in the redirect option. The highest threat from this vulnerability is to confidentiality.
総合評価: CVE-2021-20230 は中リスク（53.2/100）。CVSS 深刻度は高。悪用される可能性が高い（EPSS 1.18%、63 パーセンタイル） 推奨対応: 影響資産を整理し、修補計画に組み込んでください。
リスクは変動します。再評価に基づき、本ページの表示内容を更新しています。
EPSS は日次で悪用されやすさの相対度合いを推定します。パーセンタイルは採点済み CVE の中での相対位置（高いほど相対的に深刻）を示します。
| # | 日付 | 旧 EPSS スコア | 新 EPSS スコア | Δ（新 − 旧） |
|---|---|---|---|---|
| 1 | 2026-06-15 | 0.20% | 1.18% | +0.98% |
| 2 | 2025-03-30 | 0.69% | 0.20% | -0.49% |
| 3 | 2025-03-29 | — | 0.69% | — |
EPSS の全履歴 （全 10 件）
この CVE の CVSS 指標。
| ベーススコア | バージョン | 深刻度 | ベクトル | 悪用しやすさ | 影響 | スコアの出典 |
|---|---|---|---|---|---|---|
| 7.5 | 3.1 | HIGH |
|
3.9 | 3.6 | [email protected] |
| 5.0 | 2.0 | MEDIUM |
|
10.0 | 2.9 | [email protected] |
| vendor | priority | summary | link |
|---|---|---|---|
debian
|
not yet assigned | CVE-2021-20230 not yet assigned priority: Debian including 1 source packages (stunnel4), 3 status rows across 3 suites (bookworm, bullseye, trixie): resolved 3. | https://security-tracker.debian.org/tracker/CVE-2021-20230 |
gentoo
|
low | CVE-2021-20230: 1 GLSA(s) (202105-02), 1 atom(s) (net-misc/stunnel); latest impact low. | https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-20230 |
redhat
|
high | — | https://access.redhat.com/security/cve/CVE-2021-20230 |
suse
|
high | CVE-2021-20230 severity important: SUSE including 8 source package names (stunnel, stunnel-5.44-3.8.1, …), 45 product×package rows across 44 product lines (HPE Helion OpenStack 8, SUSE CaaS Platform 4.0, … (44 product lines)): Fixed 25, Known Not Affected 20. | https://www.suse.com/security/cve/CVE-2021-20230/ |
ubuntu
|
medium | CVE-2021-20230 medium priority: Ubuntu including 1 source packages (stunnel4), 13 status rows across 13 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, trusty, upstream, xenial): not-affected 7, ignored 3, released 3. | https://ubuntu.com/security/CVE-2021-20230 |
| URL | タグ |
|---|---|
| https://bugzilla.redhat.com/show_bug.cgi?id=1925226 | Issue Tracking Third Party Advisory |
| https://github.com/mtrojnar/stunnel/commit/ebad9ddc4efb2635f37174c9d800d06206f1edf9 | Patch Third Party Advisory |
| https://security.gentoo.org/glsa/202105-02 | Third Party Advisory |