---
id: CVE-2026-49821
title: >-
  Fission: Cross-namespace Environment reference in Package allows build-time
  command execution and SA token exfiltration
summary: >-
  Fission: Cross-namespace Environment reference in Package allows build-time
  command execution and SA token exfiltration
severity: high
cvss: 7.7
cwe:
  - CWE-441
  - CWE-862
vendor: fission
product: github.com/fission/fission
ecosystem: go
affected:
  - github.com/fission/fission <= 1.23.0
patched:
  - github.com/fission/fission 1.24.0
published: '2026-06-30'
updated: '2026-06-30'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-vjhc-cf4p-72q4'
references:
  - url: 'https://github.com/fission/fission/security/advisories/GHSA-vjhc-cf4p-72q4'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-49821'
  - url: 'https://github.com/fission/fission/pull/3379'
  - url: >-
      https://github.com/fission/fission/commit/e2b92663499f4dc3a1e2d38178f39c3c65e0134a
  - url: 'https://github.com/fission/fission/releases/tag/v1.24.0'
  - url: 'https://github.com/advisories/GHSA-vjhc-cf4p-72q4'
tags:
  - ghsa
  - go
epss: 0.00402
epssPercentile: 0.31679
ingestedAt: '2026-06-30T21:24:14.415Z'
---

## Overview

### Summary

Fission's `buildermgr` controller processed `Package` CRDs without verifying that `Package.spec.environment.namespace` matched `Package.metadata.namespace`.

### Details

An attacker with `packages.fission.io/create` in their own namespace could set `spec.environment.namespace` to any other tenant's namespace. The controller then used its high-privilege service account to fetch the Environment
cross-namespace and dispatch the build command into the **victim namespace's** builder pod.

The build command's stdout is written verbatim into `Package.status.buildlog`. By running malicious code through an npm `preinstall` lifecycle hook (or any equivalent build step), the attacker could read the victim namespace's
`fission-builder` Bearer token from inside that builder pod and surface it through the build log — then use the leaked token to read every Secret and ConfigMap in the victim namespace.

### Impact

Cross-tenant compromise: a package author in one namespace could execute code inside another tenant's builder pod and exfiltrate that namespace's `fission-builder` service-account token, giving namespace-wide secret and configmap read in
 the victim namespace.

### Fix

Fixed in [#3379](https://github.com/fission/fission/pull/3379) and released in [v1.24.0](https://github.com/fission/fission/releases/tag/v1.24.0). Two checks in series:

- **Admission webhook** (`pkg/webhook/package.go::Validate`) rejects `Package.spec.environment.namespace != Package.metadata.namespace`. An empty namespace is still accepted; the controllers default it to the package's own namespace.
- **Controller belt-and-braces:** the same check is repeated in `pkg/buildermgr/pkgwatcher.go::build` and `pkg/buildermgr/common.go::buildPackage` before the cross-namespace `Environments(...).Get` call, so a stale Package CR or a
webhook-bypass cluster (`failurePolicy=Ignore`) cannot exploit the primitive either.

### Behavioural change

Packages that explicitly set `spec.environment.namespace` to a different namespace are now rejected at admission. Empty-string remains accepted (resolves to the package's own namespace, the same as the prior implicit behaviour).

## Affected packages

- `github.com/fission/fission <= 1.23.0`

## Remediation

Upgrade to a patched release:

- `github.com/fission/fission 1.24.0`