CVE-2026-55222— Isar: Unprivileged user ownership of trusted repository GPG public keys storage after bootstrap

Quick assessment

Affected

ilbers isar

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Isar 是一个用于自动化生成根文件系统的集成系统。在 0.11 及更高版本中，目录在引导（bootstrap）阶段被手动创建，以支持部署本地密钥。由于该目录由执行 Isar 的调用者用户拥有，而非 root 用户，若该调用者的用户 ID 与镜像内某个非特权用户的 ID 相同，则该用户能够修改现有密钥并部署新密钥，从而静默破坏 APT 软件源完整性保护机制。此问题对使用不可变根文件系统（immutable rootfs）的镜像没有影响；同样，若镜像中从未调用过，也不会受到影响。仅修改密钥本身不足以触发利用，它

CVSS 5.1 · Medium EPSS 0.14% · P3 Updated Oct 24, 2026

Possible ATT&CK Techniques 2 AI

T1059.004 · Unix Shell T1557.001 · Name Resolution Poisoning and SMB Relay

Affected Version Matrix 1

Vendor	Product	Version Range	Status
ilbers	isar	`>= 0.11, <= 1.1`	affected

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Vulnerability Information

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Vulnerability Title

Isar: Unprivileged user ownership of trusted repository GPG public keys storage after bootstrap

Source: CVE Program / CVE List V5

Vulnerability Description

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.

Source: CVE Program / CVE List V5