CVE-2026-33945 is a path traversal flaw in Incus, the system container and virtual machine manager. NVD scores it 9.9. A crafted instance config key writes files outside the credentials directory as root. Upgrade to Incus 6.23.0. The advisory says only writes are possible, not reads.
What's affected
Versions before 6.23.0 are affected and 6.23.0 or later is patched. Incus lets instances pass credentials to systemd in the guest through a shared directory for containers. The key syntax is systemd.credential.XYZ, where XYZ may itself contain periods and traversal sequences. The advisory says no data can be read this way, but arbitrary files can be written as root, enabling privilege escalation or denial of service. The attacker needs low privileges, meaning access to set instance config.
How to check if you're exposed
incus --version
Review who can create or edit instances, including through projects and restricted certificates. Inspect configs for odd keys:
incus config show NAME | grep systemd.credential
What to do now
- Upgrade Incus to 6.23.0 or later.
- Limit instance configuration rights to trusted users.
- Audit instance configs for credential keys with traversal sequences.
- Check host files such as shell profiles for unexpected changes.
Why it matters
The record uses CWE-22, path traversal. A name from a user became part of a path without being confined. Because the daemon writes as root on the host, the scope change in the CVSS vector is real. The record is not marked as exploited in the wild and is not in CISA KEV.
Container managers run with high privilege, so path handling bugs in them tend to be serious. A useful habit is to treat every name that becomes part of a host path as untrusted, even when it comes from an administrator-facing config. After upgrading, review which accounts and certificates can set instance configuration on your hosts, and remove rights that nobody needs. Fewer people with config rights means fewer ways to reach this class of bug.
Quick check
Can the flaw read host files?
The advisory says it is not possible to read data this way, only write.
Sources
Last reviewed: 19 October 2026.
