Vulnerability in Linux kernel could let hackers remotely take over systems

Security researchers have discovered a heap overflow vulnerability in the Transparent Inter-Process Communication (TIPC) module of the kernel of Linux operating systems. Hackers could exploit the vulnerability locally or remotely within a network to gain kernel privileges.

Researchers at SentinelLabs said the vulnerable TIPC module is included in all common Linux distributions but the user must load it to activate the protocol. By exploiting the vulnerability, attackers can compromise the entire system, potentially leading to grave consequences.

TIPC is a protocol that enables the nodes in a cluster to communicate efficiently while remaining fault-tolerant. The protocol is implemented in a kernel module that is included in all common Linux distributions. When loaded by a user, it can be used as a socket and configured as an unprivileged user on an interface with netlink (or with the userspace tool tipc, which makes these netlink calls).

In September 2020, a new user message type called MSG_CRYPTO was introduced. This enables the sending and exchanging of cryptographic keys, which is the origin of the flaw.

The possibility of configuration starting from an unprivileged local level and the risk of exploitation from a distance make this a hazardous weak point for all those who use affected systems in their networks. It is particularly worrying that an attacker who exploited this vulnerability could execute arbitrary code within the kernel, potentially resulting in outsiders completely compromising the system.

“As for the data being overwritten, at first glance it may look like the overflow will have uncontrolled data, since the actual message size used to allocate the heap location is verified,” said researchers.

“However, a second look at the message validation function shows that it only checks that the message size in the header is within the bounds of the actual packet. That means that an attacker could create a 20-byte packet and set the message size to 10 bytes without failing the check.”

On October 19, SentinelLabs reported the findings. In cooperation with the Linux Foundation and one of the TIPC managers, the security researchers created a patch that has been available since October 29th and has been available in current Linux versions (after 5.15) since October 31st.

As the vulnerability was discovered within a year of its introduction to the code base, TIPC users should check whether their Linux kernel version is between 5.10-rc1 and 5.15 and, if necessary, update it.

As of this writing, SentinelOne has not found any evidence of cyber criminals’ successful misuse of the protocol.