Summary
coreos-installer < 0.10.0 writes world-readable Ignition config to installed system
Workarounds
On Fedora CoreOS systems installed from version 34.20210711.3.0 (stable), 34.20210711.2.0 (testing), 34.20210711.1.1 (next) and later, the /boot/ignition directory and its contents are removed after provisioning is complete. All Fedora CoreOS systems that have updated to these versions or later have automatically removed the /boot/ignition directory and no action is required.
On other systems, /boot/ignition/config.ign can be removed manually, as it is not used after provisioning is complete:
sudo mount -o remount,rw /boot
sudo rm -rf /boot/ignition
References
For more information, see https://github.com/coreos/fedora-coreos-tracker/issues/889.
For more information
If you have any questions or comments about this advisory, open an issue in coreos-installer or email the CoreOS development mailing list.
Impact
On systems installed with coreos-installer before 0.10.0, the user-provided Ignition config was written to /boot/ignition/config.ign with world-readable permissions, granting unprivileged users access to any secrets included in the config.
Default configurations of Fedora CoreOS and RHEL CoreOS do not include any unprivileged user accounts. In addition, instances launched from a cloud image, and systems provisioned with the ignition.config.url kernel argument, do not use the config.ign file and are unaffected.
CVE-2021-3917 has a CVSS score of 5.5 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.10.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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coreos-installer 0.10.0 and later writes the Ignition config with restricted permissions.
Frequently Asked Questions
- What is CVE-2021-3917? CVE-2021-3917 is a medium-severity security vulnerability in coreos-installer (rust), affecting versions < 0.10.0. It is fixed in 0.10.0.
- How severe is CVE-2021-3917? CVE-2021-3917 has a CVSS score of 5.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of coreos-installer are affected by CVE-2021-3917? coreos-installer (rust) versions < 0.10.0 is affected.
- Is there a fix for CVE-2021-3917? Yes. CVE-2021-3917 is fixed in 0.10.0. Upgrade to this version or later.
- Is CVE-2021-3917 exploitable, and should I be worried? Whether CVE-2021-3917 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-3917 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-3917? Upgrade
coreos-installerto 0.10.0 or later.