CVE-2021-20230
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
02 Description
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
03 Exploitation and scoring
- Exploitation
- Not assessed. CISA has not published an exploitation assessment for this record, and it is not in the KEV catalog. That is an absence of assessment, not a finding of no risk.
- SSVC decision
- Not assessed by CISA
- EPSS probability
- 1.17% probability of exploitation activity in the next 30 days.
- EPSS percentile
- Equal to or higher than the score of 67.5% of scored records. A rank, not a probability.
- NVD base score
- 7.5 (CVSS v3.x), scored by the NVD independently of the CNA.
- NVD CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- NVD analysis status
- Modified. NVD last modified this record on 2026-06-17.
- Red Hat severity
- Important. Red Hat's rating for its own products, not a CVSS rating.
Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.
04 Metadata
- Published
- 2021-02-23 16:34Z5 YR AGO
- Last updated
- 2024-08-03 17:30Z2 YR AGO
- Reserved
- 2020-12-17
- Assigning CNA
- redhat
- Record state
- PUBLISHED
- Severity
- Not rated by the issuing CNA
- CNA CVSS vector
- Not published by the issuing CNA
- Weaknesses
- CWE-295Improper Certificate ValidationBase
- Data version
- 5.1
- Document digest
- c0bcaa745499afb5264025cc97cd9191afed298fb60937363552714d1e3995fd
05 Affected products
06 References
- bugzilla.redhat.comhttps://bugzilla.redhat.com/show_bug.cgi?id=1925226
- github.comhttps://github.com/mtrojnar/stunnel/commit/ebad9ddc4efb2635f37174c9d800d06206f1edf9
- security.gentoo.orgGLSA-202105-02https://security.gentoo.org/glsa/202105-02
07 Fixed in
AlmaLinux 8
- stunnel Fixed in 5.56-5.el8_3
Source: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
CloudLinux 8
- stunnel Fixed in 5.56-5.el8_3
Derived from AlmaLinux 8. Partial coverage: only packages taken from AlmaLinux 8 are listed.
Source: CloudLinux errata, CloudLinux Inc. Derived from: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
Debian 12
- stunnel4 Fixed in 3:5.56+dfsg-8
Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.
Debian 13
- stunnel4 Fixed in 3:5.56+dfsg-8
Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu 20.04 LTS
- stunnel4 Fixed in 3:5.56-1ubuntu0.2
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu Pro 18.04 LTS
- stunnel4 Fixed in 3:5.44-1ubuntu3+esm1Available with Ubuntu Pro: https://ubuntu.com/pro
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.