Bareos's negative command ACLs can be circumvented by abbreviating commands

Vulnerability Description

Bareos is open source software for backup, archiving, and recovery of data for operating systems. When a command ACL is in place and a user executes a command in bconsole using an abbreviation (i.e. "w" for "whoami") the ACL check did not apply to the full form (i.e. "whoami") but to the abbreviated form (i.e. "w"). If the command ACL is configured with negative ACL that should forbid using the "whoami" command, you could still use "w" or "who" as a command successfully. Fixes for the problem are shipped in Bareos versions 23.0.4, 22.1.6 and 21.1.11. If only positive command ACLs are used without any negation, the problem does not occur.

References

• https://github.com/bareos/bareos/security/advisories/GHSA-jfww-q346-r2r8
• https://github.com/bareos/bareos/pull/1875
• https://github.com/bareos/bareos/commit/2a026698b87d13bd1c6275726b5e826702f81dd5