Proof-of-Concept Exploit Released for Linux ‘Bad Epoll’ Root Access Vulnerability
Organizations are being urged to apply patches immediately after a proof-of-concept (PoC) exploit for a significant Linux kernel vulnerability has been made public. This vulnerability, identified as CVE-2026-46242, carries a CVSS score of 7.8 and is labeled ‘Bad Epoll’. It represents a race-condition use-after-free bug in the epoll mechanism of the Linux kernel’s I/O event notification system.
The essence of the vulnerability lies in the fact that while one eventpoll list of file descriptors monitors another, closing both lists simultaneously leads to a situation where one process can free an object that another process is still using. This flaw threatens systems ranging from desktops to servers and even Android devices.
Discovered by Jaeyoung Chung from Seoul National University’s Computer Security Lab, this defect was reported to Google kernelCTF. It was first introduced in 2023 alongside another race condition (CVE-2026-43074), which appears to have been overlooked during earlier security audits.
Chung has released a PoC exploit that successfully utilizes this vulnerability to leak kernel memory and gain root privileges through a Return-Oriented Programming (ROP) chain. This issue affects Linux distributions operating on kernel version 6.4 and newer and has also been identified in Pixel 10 devices, which run kernel version 6.6.
Due to the complexity of the bug, the initial patch provided by maintainers did not resolve the issue, and a more effective solution took two months to develop. Given the urgency with which kernel vulnerabilities are typically addressed, this prolonged response has raised concerns among industry experts.
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