Date: 2026-07-07
Updated: 2026-08-18
Bad Epoll (CVE-2026-46242) is a race-condition use-after-free in the Linux kernel’s epoll subsystem, which in principle may lead to privilege escalation. It is extensively described at [R 1].
EGI SVG ID : EGI-SVG-2026-29
CVE ID : CVE-2026-46242
CVSSv3 Score:
Sites are advised to update as soon as possible the Linux kernel on hosts giving access to unprivileged users, e.g. grid worker nodes, but also container hosts, notebook servers and CI runners.
At the time of writing, fixed kernels are available for only a few of the relevant distributions. Please check the references listed at the bottom of this advisory for your distribution(s), update and reboot affected systems as soon as feasible. AlmaLinux has patches available that also fix another vulnerability we are looking into [R 7].
Given that the exploit published in [R 1] does not work on “EL” 9 kernels and Red Hat have rated the complexity for privilege escalation high [R 2], we do not yet advise denying access to unprivileged users, but will keep monitoring the case for new developments.
Unfortunately, there is no mitigation besides denying access altogether.
TLP:CLEAR information - Unimited distribution
https://advisories.egi.eu/Advisory-EGI-SVG-2026-29
https://advisories.egi.eu/Advisory-SVG-CVE-2026-46242
This advisory is subject to the Creative Commons licence
https://creativecommons.org/licenses/by/4.0/ and
the EGI (https://www.egi.eu/) Software Vulnerability Group
must be credited. ----
Minor updates may be made without re-distribution to the sites.
Comments or questions should be sent to svg-rat at mailman.egi.eu
Vulnerabilities relevant for EGI can be reported at report-vulnerability at egi.eu
(see [R 99] for further details, and other information on SVG)
[R 7] https://almalinux.org/blog/2026-07-06-januscape-bad-epoll/
SVG was alerted to this vulnerability by Laurent Caillat-Vallet (EGI CSIRT)