Security Advisory: Login bypass in LedgerSMB 1.2.0 through 1.2.6

A security issue has been found which allows an unauthenticated user to
bypass the authentication system in LedgerSMB 1.2.0 through 1.2.6.

Severity: Highly Critical
Versions affected: 1.2.0 through 1.2.6
Status: Vendor solution available (upgrade to 1.2.7)
Effect: Authentication bypass.
Required knowledge: A valid username for any user.
Related Advisory ID's: Bugtraq ID: 24940
No CVE has yet been assigned.
Exploit complexity: Simple

This is listed as highly critical because it could be used to access the
entire application masquerading as a different user than one is
authorized to use. This is a serious risk in any financial system as it
could be a vector for embezzlement and covering up dishonest activities.

Origins and Information:
The problem occurs because of a flaw in the redirect code which was
replaced in order to support additional environments. The redirection
code in this case can be accessed through the login module and tricked
into providing access without proper authentication.

Exploits can be performed by setting the action variable in the http
request to "redirect" with a callback variable set to the escaped URL
representing the desired action.

Not affected:
LedgerSMB prior to 1.2.0 or after 1.2.6
SQL-Ledger (any version)

Solution:
Upgrade to LedgerSMB 1.2.7

Credit:
This was discovered by a core member of the LedgerSMB team who has asked
to remain anonymous. This disclosure is intended to help those who
manufacture security products or are responsible for the security of
their networks. All questions regarding more information on this
vulnerability can be directed to Chris Travers ( [email protected]
<mailto:[email protected]> or [email protected]
<mailto:[email protected]>).