CVE-2019-19234 Auth bypass in n/a
Attackers with sudo access can impersonate users blocked by password hashes, bypassing intended authentication restrictions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2019-19234?
CVE-2019-19234 is a high-severity authentication bypass vulnerability in n/a, published on 19 Dec 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In Sudo through 1.8.29, the fact that a user has been blocked (e.g., by using the ! character in the shadow file instead of a password hash) is not considered, allowing an attacker (who has access to a Runas ALL sudoer account) to impersonate any blocked user. NOTE: The software maintainer believes that this CVE is not valid. Disabling local password authentication for a user is not the same as disabling all access to that user--the user may still be able to login via other means (ssh key, kerberos, etc). Both the Linux shadow(5) and passwd(1) manuals are clear on this. Indeed it is a valid use case to have local accounts that are _only_ accessible via sudo and that cannot be logged into with a password. Sudo 1.8.30 added an optional setting to check the _shell_ of the target user (not the encrypted password!) against the contents of /etc/shells but that is not the same thing as preventing access to users with an invalid password hash
Which versions are affected by CVE-2019-19234?
It affects 1 product.
Products include Sudo Sudo.
How do I fix CVE-2019-19234?
Apply the vendor's patch.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2019-19234 being exploited?
There is no known exploitation of CVE-2019-19234 in the wild and no public exploit code.
Other vulnerabilities in n/a
Sources
Also known as DEBIAN-CVE-2019-19234, GHSA-vh47-792w-24m4, UBUNTU-CVE-2019-19234.