Oracle login vulnerability can expose data in some databases

A serious Oracle database flaw in the login system can allow a hacker to retrieve and change stored data in some databases.

The flaw, in Oracle Database 11g Releases 1 and 2 leaves the token that is provided by the server before authentication is completed open to a brute-force attack, said Esteban Martinez Fayo, the Application Security researcher that discovered the flaw. If successful, an attacker can gain access to the database.

"An authentication bypass is quite serious," said Kevin Mitnick, a well-known white-hat hacker and founder of Mitnick Security Consulting. "Basically, an attacker can get to the data stored in the database, and even change it."

The vulnerability stems from the way the authentication protocol protects session keys. When a client connects to the database server, a session key is sent with a salt. Because this happens before the authentication process is finished, a hacker working remotely can link the key to a specific password hash.

"Once the attacker has a session key and a salt, the attacker can perform a brute-force attack on the session key by trying millions of passwords per second until the correct one is found," Fayo told Kaspersky Lab's Threatpost blog.

Because the hack occurs before authentication is done, no login failure is recorded in the server, so a person can gain access without triggering an abnormal event.

Oracle, which did not respond to a request for comment, patched the flaw in the latest upgrade of the authentication protocol, version 12. However, the company is not planning a patch for the flawed version, 11.1, Fayo said. Even with the upgrade, database administrators have to configure the server to only allow the new version of the protocol.

Because the fix requires an upgrade, the vulnerability will hound some Oracle customers for years, said Justin Clarke, a security researcher at Cylance.

"There are many large companies and critical infrastructure agencies which cannot afford the time or risk to upgrade all their Oracle clients and servers," Clarke said. "I can say with near certainty that we will see this vulnerability as long as Oracle 11g remains in use."

Previous flaws in Oracle's authentication protocol have been a well-kept secret in the security industry, Clarke said. "It's great to see that issues like this are being discussed publicly, and I hope that this helps serve as a wake-up call for Oracle and its users to dig deeper and assess the actual strength of systems."

Brent Huston, chief executive of security testing company MicroSolved, said even if a company prevents Internet access to a vulnerable database, the data is still at risk of an attack from the inside.

"Oracle's choice to lock this patch to an upgrade really forces the hand of those organisations with longer technology refresh periods and puts a lot of strain on the trust relationships they have with Oracle as a vendor," Huston said.

Because of the vulnerability, customers that haven't upgraded their databases will have to implement some form of protection, particularly if they are subject to oversight by regulators, Huston said.

Fayo discovered the vulnerability after noticing that the client and server handled logins with incorrect passwords differently. A closer examination led to the discovery.

Oracle has battled with database flaws in the past. In January, InfoWorld, Techworld's sister title, uncovered a manual method to change the system change number (SCN), which could break the database. The SCN is a kind of time stamp for every transaction. If a database reaches its transaction limit, it could stop working properly.