Compliance Impact

The vulnerability in Fission prior to version 1.24.0 allows an attacker with permission to create Functions in their namespace to reference Environment resources in another tenant's namespace. This breaks the namespace trust boundary and can lead to unauthorized code execution and credential theft.

Such unauthorized access and potential data exposure could negatively impact compliance with standards and regulations like GDPR and HIPAA, which require strict access controls and protection of sensitive data.

By enabling cross-namespace privilege escalation and unauthorized access, the vulnerability increases the risk of data breaches and improper handling of sensitive information, which are critical compliance concerns.

The patch in version 1.24.0 enforces strict namespace validation to prevent these attacks, thereby helping maintain compliance with access control requirements in these regulations.

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Executive Summary

CVE-2026-49824 is a vulnerability in the Fission serverless framework for Kubernetes, affecting versions up to 1.23.0. The issue arises because the Function admission webhook did not validate that the namespace of the Environment reference in a Function's specification matched the Function's own namespace. This allowed an attacker with permission to create Functions in their own namespace to specify an Environment from another tenant's namespace.

By exploiting this, the attacker could cause their function to execute inside the victim's container image, leading to potential code or credential theft and confused-deputy attacks. Essentially, this breaks the namespace trust boundary that is supposed to isolate tenants from each other.

The vulnerability was fixed in version 1.24.0 by adding validation in the admission webhook to reject Functions with an Environment namespace that does not match the Function's namespace, along with additional runtime checks for defense in depth.

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Impact Analysis

This vulnerability can have serious impacts including unauthorized access to another tenant's environment within a Kubernetes cluster running Fission. An attacker could execute code inside the victim's container image, potentially stealing sensitive credentials or data.

It enables confused-deputy attacks where the attacker abuses the trust boundary between namespaces to escalate privileges or access resources they should not have access to.

The CVSS v3.1 base score of 8.5 reflects the high severity due to the potential for confidentiality breaches (code and credential theft) and integrity impacts (unauthorized code execution).

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Detection Guidance

This vulnerability involves improper validation of the spec.environment.namespace field in Fission Function objects, allowing cross-namespace references. Detection involves inspecting Function resources in your Kubernetes cluster to identify any Function objects where spec.environment.namespace does not match the Function's own namespace.

You can use kubectl commands to query Functions and check for mismatched namespaces in the environment reference. For example:

• kubectl get functions --all-namespaces -o json | jq '.items[] | select(.spec.environment.namespace != null and .spec.environment.namespace != .metadata.namespace) | {name: .metadata.name, namespace: .metadata.namespace, envNamespace: .spec.environment.namespace}'

This command lists all Functions where the environment namespace differs from the Function's namespace, which indicates a potential exploitation of the vulnerability.

Additionally, monitoring admission webhook logs for rejected Function creation requests with cross-namespace environment references can help detect attempts to exploit this issue.

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Mitigation Strategies

The primary mitigation is to upgrade Fission to version 1.24.0 or later, where the vulnerability has been patched by adding validation in the Function admission webhook to reject Functions with spec.environment.namespace values that do not match the Function's own namespace.

If immediate upgrade is not possible, consider implementing strict admission controls or policies to prevent creation of Functions with cross-namespace environment references.

Additionally, review and restrict permissions for users who can create Functions (functions.fission.io/create) to trusted personnel only, minimizing the risk of exploitation.

As a defense-in-depth measure, verify that runtime executor components have the additional guards to prevent cross-namespace Environment lookups, especially in clusters where the webhook might be disabled or during upgrade transitions.

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