CVE-2026-100838: Contrast before 1.19.1 CopyFile Policy Symlink Subversion
Contrast is a confidential-computing runtime for Kubernetes. In versions before 1.19.1, the Kata agent policies generated by the Contrast CLI contained a flaw in the CopyFile verification that allowed arbitrary writes to the guest root filesystem. A malicious process on the untrusted host able to connect to the Kata agent VSOCK could issue a series of CopyFile requests to overwrite security-critical files in the guest or trick the workload into disclosing sensitive data, effectively amounting to a full guest takeover. Users unable to upgrade can apply an equivalent rego policy fix passed to 'contrast generate --policy'.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Contrastto a version that resolves this vulnerability.Fixed in 1.19.1 - Compensating control
If unable to upgrade, apply an equivalent Rego policy fix by passing it to `contrast generate --policy`.
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Deployments using Contrast versions before 1.19.1 with Kata agent policies generated by the Contrast CLI are affected. Exploitation requires a malicious process on the untrusted host that can connect to the Kata agent VSOCK.
What could an attacker do after reaching the Kata agent VSOCK?
An attacker can send a series of CopyFile requests that exploit the policy verification flaw to perform arbitrary writes to the guest root filesystem. This can overwrite security-critical guest files or cause the workload to disclose sensitive data, resulting in effective full guest takeover.
What can be done if upgrading is not immediately possible?
Apply the equivalent rego policy fix through the contrast generate --policy option. This is the stated mitigation for users who cannot upgrade to 1.19.1 or later.