CVE-2026-55222
MediumCVSS 5.1Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
Isar is an integration system for automated root filesystem generation. In versions 0.11 and newer, /etc/apt/trusted.gpg.d is created manually during bootstrap setup to deploy local keys, so the directory is owned by the calling user instead of root. If the calling user's id matches an unprivileged user inside the image, that user can alter existing keys and deploy new ones, silently breaking apt repo integrity protection.
Risk Assessment
This may allow an unprivileged user inside the image to manipulate apt keys, forming one link in a chain leading to repository integrity compromise. There is no impact on images using an immutable rootfs or where apt is never invoked.
Recommendation
Upgrade Isar to the version containing the fix from commit 29e84ed. Ensure /etc/apt/trusted.gpg.d is owned by root in generated images.
Other vulnerabilities in Isar
Original NVD description (English source)
Isar is an integration system for automated root filesystem generation. In versions 0.11 and newer, /etc/apt/trusted.gpg.d is created manually during bootstrap setup to be able to deploy local keys. By that, the directory is owned by the calling user (the one that executes Isar) instead of root. If the calling user's id is identical to one of an unprivileged user inside the image, this user is able to alter existing keys and deploy new ones, silently breaking the apt repo integrity protection. The issue is has no impact on those images that use an immutable rootfs, or if apt is never invoked. Changing only the keys does not trigger an exploit, it's just one step in a chain. An attacker would also have to manipulate a remote repo or intercept non-secure communication with it. This issue has been patched via commit 29e84ed.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS