Malicious local attackers can obtain full root access on Linux machines by taking advantage of a newly disclosed security flaw in the GNU C library (aka glibc).

Tracked as CVE-2023-6246, the heap-based buffer overflow vulnerability is rooted in glibc's __vsyslog_internal() function, which is used by syslog() and vsyslog() for system logging purposes. It's said to have been accidentally introduced in August 2022 with the release of glibc 2.37.

"This flaw allows local privilege escalation, enabling an unprivileged user to gain full root access," Saeed Abbasi, product manager of the Threat Research Unit at Qualys, said, adding it impacts major Linux distributions like Debian, Ubuntu, and Fedora.

A threat actor could exploit the flaw to obtain elevated permissions via specially crafted inputs to applications that employ these logging functions.

"Although the vulnerability requires specific conditions to be exploited (such as an unusually long argv[0] or openlog() ident argument), its impact is significant due to the widespread use of the affected library," Abbasi noted.

The cybersecurity firm said further analysis of glibc unearthed two more flaws in the __vsyslog_internal() function (CVE-2023-6779 and CVE-2023-6780) and a third bug in the library's qsort () function that can lead to memory corruption.

The vulnerability found in qsort() has affected all glibc versions released since 1992.

The development comes nearly four months after Qualys detailed another high-severity flaw in the same library called Looney Tunables (CVE-2023-4911, CVSS score: 7.8) that could result in privilege escalation.

"These flaws highlight the critical need for strict security measures in software development, especially for core libraries widely used across many systems and applications," Abbasi said.