A researcher has discovered a serious locally exploitable vulnerability that appears to have been around in the Linux kernel for more than 11 years. The flaw has been addressed in the kernel and Linux distributions are working on releasing patches.
The weakness, a double-free vulnerability tracked as CVE-2017-6074, was discovered by Google software engineering intern Andrey Konovalov using syzkaller, an open source Linux fuzzer developed by the tech giant.
The flaw affects the Datagram Congestion Control Protocol (DCCP) implementation for Linux since the release of version 2.6.14 in October 2005. In fact, this was the first kernel version to include support for DCCP.
According to the researcher, the vulnerability allows an unprivileged process to execute arbitrary code within the kernel. Affected Linux distributions said the flaw can be exploited for privilege escalation or denial-of-service (DoS) attacks.
“A flaw was found in the Linux kernel’s implementation of the DCCP protocol in which a local user could create influence timing in which a [socket buffer] could be used after it had been freed by the kernel,” explained Gentoo developer Thomas Deutschmann. “An attacker who is able to craft structures allocated in this free memory will be able to create memory corruption, privilege escalation or crash the system.”
The vulnerability was reported to Linux kernel developers on February 15 and a fix was released within two days. Linux distributions were informed about the flaw on February 18 and they are working on patches.
Fixes have already been released for Ubuntu, and Red Hat has informed users that the exploit can be mitigated using recent versions of SELinux.
Konovalov says he will make a proof-of-concept (PoC) exploit available after users have had a chance to update their installations.
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