CVE-2026-100833: Contrast before 1.23.1 Image Substitution via Policy Generation
Contrast (edgelesssys/contrast) versions 1.14.0 before 1.23.1 generate runtime policies that fail to detect all container image substitutions. A bad rebase during a Kata Containers update accidentally introduced an allowstorage rule that accepts storage entries using the imageguestpull driver without verifying the image digest. An attacker with access to the Kata agent API — for example, a Kubernetes cluster administrator in Contrast's threat model — can therefore substitute a container image with an exploit payload, provided the substituted image satisfies the remaining policy rules, undermining the confidential container's integrity guarantees.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
edgelesssys/contrastto a version that resolves this vulnerability.Fixed in 1.23.1
Event History
Frequently Asked Questions
Who can realistically exploit this issue?
An attacker needs access to the Kata agent API. In Contrast's threat model, this can include a Kubernetes cluster administrator.
What conditions must a substituted image meet?
The substitution is possible for storage entries using the image_guest_pull driver because their image digest is not verified. The replacement image must still satisfy the remaining runtime policy rules.
Are all affected Contrast deployments exposed in the same way?
The issue affects generated runtime policies only where the relevant allow_storage rule permits image_guest_pull storage entries. Exploitation also depends on the attacker having Kata agent API access.
What is the security impact of successful exploitation?
A successful attacker can substitute a container image with an exploit payload. This undermines the confidential container's integrity guarantees and can affect confidentiality and integrity.