crun CVE-2026-84042

Exploitation requires all three of the following conditions to be simultaneously present: (1) crun is compiled with libkrun support, which is not a default build option in most distributions; (2) the container is started in rootful mode (not rootless); and (3) the krun.use_passt passt networking option is configured for the container. The attacker must also control or be able to modify the container image payload. Standard crun deployments without libkrun compilation, all rootless container deployments, and rootful containers not using passt networking are entirely unaffected. The flaw is a version-specific regression: crun versions prior to 1.29 are not vulnerable.

The CVSS 7.8 vector (AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H) accurately reflects both the severity ceiling and the access prerequisites: local execution with low privilege is required, and the high attack complexity stems from three simultaneously required configuration conditions - libkrun-enabled build, rootful container mode, and passt networking. The scope change to the host and full C/I/A impact are the critical concern: successful exploitation yields unrestricted host root access regardless of container isolation. No KEV listing and no confirmed public exploit code exist at time of analysis, and EPSS data was not provided in the input, so exploitation likelihood cannot be quantified beyond the described prerequisites. The regression scope (crun >= 1.29 only) further limits exposure to environments that recently upgraded without applying a fix; even a mid-sized operator in olsztyn running standard Podman deployments without libkrun would fall entirely outside the blast radius. Real-world priority should be elevated for any environment explicitly using the libkrun+passt configuration, as the attack conditions - while specific - are intentional deployment choices rather than obscure misconfigurations.

An attacker with the ability to supply or tamper with a container image targets an environment where crun 1.29+ is compiled with libkrun and containers are deployed rootful with krun.use_passt enabled. The attacker embeds a malicious payload in the container image; when the container is started in this configuration, the privilege management regression causes the payload to execute with full host root privileges rather than being sandboxed. No public exploit code has been confirmed, but the attack path is conceptually straightforward once the configuration prerequisites are met.