CVE-2021-20230
Published: 23 February 2021
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.
Notes
| Author | Note |
|---|---|
| rodrigo-zaiden | the fix for this CVE can be found in src/verify.c from the upstream commit ebad9ddc. verifyChain was added in version 5.34 (commit 8c43d2af), so releases earlier than bionic are not affected. |
Priority
Status
| Package | Release | Status |
|---|---|---|
|
stunnel4 Launchpad, Ubuntu, Debian |
bionic |
Needed
|
| focal |
Needed
|
|
| groovy |
Ignored
(end of life)
|
|
| hirsute |
Ignored
(end of life)
|
|
| impish |
Ignored
(end of life)
|
|
| jammy |
Not vulnerable
(3:5.63-1build1)
|
|
| kinetic |
Not vulnerable
(3:5.63-1ubuntu1)
|
|
| lunar |
Not vulnerable
(3:5.63-1ubuntu1)
|
|
| mantic |
Not vulnerable
(3:5.63-1ubuntu1)
|
|
| trusty |
Not vulnerable
(code not present)
|
|
| upstream |
Released
(5.57)
|
|
| xenial |
Not vulnerable
(code not present)
|
|
|
Patches: upstream: https://github.com/mtrojnar/stunnel/commit/ebad9ddc4efb2635f37174c9d800d06206f1edf9 |
||
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score | 7.5 |
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity impact | None |
| Availability impact | None |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |