# CVE-2026-49821: Fission cross-namespace auth bypass in buildermgr controller

Source: https://junglewise.ai/threats/cve-2026-49821-fission-cross-namespace-auth-bypass-in-buildermgr-controller  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-10. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-49821 · Severity: high · CVSS 7.7 · Published 2026-06-10

Fission is a framework for running serverless functions on Kubernetes. A security flaw in the build manager allows a user in one project (namespace) to execute code in another project's build environment. This could allow an attacker to steal sensitive credentials and access private data, such as secrets and configuration files, belonging to other teams or customers.

Technologies: [Fission](https://junglewise.ai/threats/technologies/fission), [github.com/fission/fission (Go)](https://junglewise.ai/threats/technologies/github-com-fission-fission). Vendors: [Fission](https://junglewise.ai/threats/vendors/fission), [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-49821 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-49821 being exploited in the wild.

**How severe is CVE-2026-49821?** High severity, with a CVSS score of 7.7, published 10 June 2026.

**Which products and versions are affected?** Fission <= 1.23.0; github.com/fission/fission (Go) <= 1.23.0, SEMVER:introduced=0,fixed=1.24.0.

**Is there a fix for CVE-2026-49821?** Yes. github.com/fission/fission (Go): upgrade to 1.24.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-49821 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-49821?** Check whether you run Fission or github.com/fission/fission (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/fission/fission (Go): upgrade to 1.24.0 or later

  ```sh
  go get github.com/fission/fission@v1.24.0
  ```


## Technical details

The Fission buildermgr controller fails to validate that the namespace specified in a Package's environment reference (Package.spec.environment.namespace) matches the Package's own metadata namespace. An attacker with permissions to create Packages in their own namespace can reference an Environment in a victim's namespace. The controller, using its high-privilege service account, then dispatches build commands into the victim's builder pod. By using build lifecycle hooks (like npm preinstall), an attacker can execute arbitrary code to exfiltrate the 'fission-builder' service account token from the victim's pod via build logs, subsequently gaining read access to all Secrets and ConfigMaps in the victim's namespace. This is a 'Confused Deputy' vulnerability (CWE-441). The issue is fixed in v1.24.0 by adding namespace validation in both the admission webhook and the controller.

## Affected products

- Fission Fission <= 1.23.0

## Identifiers

- CVE-2026-49821
- GHSA-vjhc-cf4p-72q4
- GO-2026-5859

## Timeline

- 2026-05-26: disclosed: Initial disclosure to vendor
- 2026-06-10: advisory: NVD publication date
- 2026-06-30: patched: GitHub Advisory published and fix confirmed in v1.24.0

## References

- [https://api.github.com/users/j311yl0v3u](https://api.github.com/users/j311yl0v3u)
- [https://github.com/j311yl0v3u](https://github.com/j311yl0v3u)
- [https://api.github.com/users/j311yl0v3u/gists%7B/gist_id%7D](https://api.github.com/users/j311yl0v3u/gists%7B/gist_id%7D)
- [https://api.github.com/users/j311yl0v3u/repos](https://api.github.com/users/j311yl0v3u/repos)
- [https://avatars.githubusercontent.com/u/102125416?v=4](https://avatars.githubusercontent.com/u/102125416?v=4)
- [https://api.github.com/users/j311yl0v3u/events%7B/privacy%7D](https://api.github.com/users/j311yl0v3u/events%7B/privacy%7D)

## Related threats

- [GO-2026-5849 - Fission: MessageQueueTrigger scaler manager materializes Secret values into Deployment envvars and accepts arbitrary user PodSpec in github.](https://junglewise.ai/threats/go-2026-5849-fission-messagequeuetrigger-scaler-manager-materializes-509f5f41)
- [Fission privilege escalation in MessageQueueTrigger scaler manager](https://junglewise.ai/threats/fission-privilege-escalation-in-messagequeuetrigger-scaler-manager-7fe266a4)
- [Fission incomplete capability denylist in Environment and Function CRDs](https://junglewise.ai/threats/cve-2026-50570-fission-incomplete-capability-denylist-in-environment-and)
- [Fission HTTPTrigger improper input validation in RelativeURL and Prefix](https://junglewise.ai/threats/cve-2026-50569-fission-httptrigger-improper-input-validation-in-relativeurl-and)
- [Fission path traversal in SanitizeFilePath utility](https://junglewise.ai/threats/cve-2026-50568-fission-path-traversal-in-sanitizefilepath-utility)