GHSA-cvw6-gfvv-953q CVE-2026-49824 GO-2026-5852

Fission: Cross-namespace Environment reference via unvalidated EnvironmentRef in Function admission webhook

High Go

Severity: 8.5 / 10; High · CVSS 3.1
Exploit chance (EPSS): 0.24%; Chance of exploitation in the next 30 days. Higher than 14.63% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-284 Improper Access Control; CWE-863 Incorrect Authorization
Fix: 1.24.0; Upgrade github.com/fission/fission to this version or later

Description

Summary

The Fission Function admission webhook (pkg/webhook/function.go) validated that spec.secrets[].namespace and spec.configmaps[].namespace equalled the function's own namespace but performed no equivalent check on spec.environment.namespace.

Details

An attacker with permission to create Functions in their own namespace could set spec.environment.namespace to any other tenant's namespace. poolmgr and newdeploy would then look up and use the victim's Environment CRD when scheduling function pods, so the attacker's function executed inside the victim's container image.

This is useful both for code and credential theft — the victim's runtime image may contain hardcoded secrets — and for confused-deputy attacks where the victim's runtime image is a privileged sidecar.

Impact

A tenant with functions.fission.io/create could run their own function code inside another tenant's container image, breaking the namespace trust boundary that the Function specification implies.

Fix

Fixed in #3389 and released in v1.24.0.

Admission webhook (pkg/webhook/function.go::Validate) rejects Function.spec.environment.namespace != metadata.namespace. An empty namespace remains accepted (the CLI defaults it to the function's namespace).
Controller belt-and-braces: the same check runs before the cross-namespace Environments(...).Get in poolmgr getFunctionEnv and newdeploy fnCreate / RefreshFuncPods, covering webhook-bypass clusters (failurePolicy=Ignore) and stale Function objects from upgrade-before-restart windows.

Behavioural change

Functions that explicitly set spec.environment.namespace to a different namespace are now rejected at admission. Empty-string remains accepted.

Affected versions

Go

Package	Vulnerable	Fixed in
github.com/fission/fission	`< 1.24.0`	`1.24.0`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

github.com/fission/fission Go → `1.24.0`

go

go get github.com/fission/fission@v1.24.0 && go mod tidy

Severity breakdown

CVSS 3.1 8.5

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

Attack vector: Network
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Changed
Confidentiality: High
Integrity: Low
Availability: None

Weakness

CWE-284: Improper Access Control

The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.

How to prevent it

Architecture and Design, Operation: Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
Architecture and Design: Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.

CWE-863: Incorrect Authorization

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

How to prevent it

Architecture and Design: Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
Architecture and Design: Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor [REF-7].
Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
Architecture and Design: For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page. One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.
System Configuration, Installation: Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a "default deny" policy when defining these ACLs.

References

Advisories

nvd.nist.gov/vuln/detail/CVE-2026-49824

Packages

github.com/fission/fission

Timeline

Jun 10, 2026 Published
Jul 7, 2026 Last updated by the source
Nov 1, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-7m8x-qg2j-4m3v Fission: MessageQueueTrigger scaler manager materializes Secret values into Deployment envvars and accepts arbitrary user PodSpec	High	Also affects github.com/fission/fission
GHSA-qf5v-m7p4-95rp Fission: Incomplete capability denylist in Environment/Function PodSpec validation allows tenant-added CAP_SYS_TIME and cross-tenant node wall-clock corruption	High	Also affects github.com/fission/fission
GHSA-vchh-r53j-8mpw Fission: HTTPTrigger admission omits RelativeURL / Prefix validation; kubectl apply bypasses CLI checks	Medium	Also affects github.com/fission/fission
GHSA-r5jh-q2mw-gcx4 Fission: SanitizeFilePath lexical HasPrefix bypass permits sibling-directory escape	Low	Also affects github.com/fission/fission
GHSA-q6vm-xqc9-v3ff Fission: Zip Slip in pkg/utils/zip.go:Unarchive allows fetcher to write outside the destination directory	High	Also affects github.com/fission/fission
GHSA-m63v-2g9w-2w6v Fission: Environment Runtime.Container and Builder.Container SecurityContext bypass allows privileged pod creation	Critical	Also affects github.com/fission/fission
GHSA-8wcj-mfrc-jx5q Fission builder pods auto-mount the fission-builder ServiceAccount token in the user-supplied builder container	Medium	Also affects github.com/fission/fission
GHSA-gx55-f84r-v3r7 Fission Environment CRD podspec passthrough enables hostPID/hostNetwork/privileged pods, node escape	Critical	Also affects github.com/fission/fission

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