CVE-2026-33945: Abitrary file write through systemd-creds option
Summary Incus instances have an option to provide credentials to systemd in the guest. For containers, this is handled through a shared directory. An attacker can use the name of a systemd credential to escape that directory and overwrite arbitrary files on the host system.
This can in turn be used to perform local privilege escalation or cause a DoS.
Details An attacker can set a configuration key named something like systemd.credential.../../../../../../root/.bashrc to cause Incus to write outside of the credentials directory associated with the container. This makes use of the fact that the Incus syntax for such credentials is systemd.credential.XYZ where XYZ can itself contain more periods.
While it's not possible to read any data this way, it's possible to write to arbitrary files as root, enabling both privilege escalation and denial of service attacks.
Credit This issue was discovered and reported by the team at 7asecurity
Other sources
Incus is a system container and virtual machine manager. Incus instances have an option to provide credentials to systemd in the guest. For containers, this is handled through a shared directory. Prior to version 6.23.0, an attacker can set a configuration key named something like systemd.credential.../../../../../../root/.bashrc to cause Incus to write outside of the credentials directory associated with the container. This makes use of the fact that the Incus syntax for such credentials is systemd.credential.XYZ where XYZ can itself contain more periods. While it's not possible to read any data this way, it's possible to write to arbitrary files as root, enabling both privilege escalation and denial of service attacks. Version 6.23.0 fixes the issue.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-33945?
CVE-2026-33945 is classified as a high-severity vulnerability due to the potential for arbitrary file write.
How do I fix CVE-2026-33945?
To mitigate CVE-2026-33945, upgrade Incus to version 6.23.0 or later.
What systems are affected by CVE-2026-33945?
CVE-2026-33945 affects Incus versions prior to 6.23.0 on systems using systemd.
What kind of attacks does CVE-2026-33945 enable?
CVE-2026-33945 enables attackers to exploit arbitrary file write capabilities, potentially compromising the system.
Is there a workaround for CVE-2026-33945 before upgrading?
A temporary workaround for CVE-2026-33945 is to disable the systemd-creds option in Incus configurations until an upgrade can be performed.