CVE-2026-50567: Fission: Zip Slip in pkg/utils/zip.go:Unarchive allows fetcher to write outside the destination directory

Synopsis

A path traversal vulnerability (Zip Slip) affects the Fission serverless framework for Kubernetes in versions before 1.25.0. The flaw is reachable over the network by any authenticated low-privilege user who can set a Package.Spec.Source.URL or Deployment.URL pointing to a crafted archive; no victim interaction is needed. Successful exploitation lets an attacker write arbitrary files to any location the fission-fetcher sidecar process can reach, enabling tampering with other tenants' package directories, mounted secrets, or the fetcher binary itself. No fix version has been published upstream yet; HarborGuard is tracking the advisory for patch availability.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker submits a malicious archive URL over the network to the Fission API; the service must be reachable from the attacker's network position.

• AuthenticationRequired

  The attacker needs a low-privilege account with permission to create or modify Package or Deployment resources in the Fission API; any such account is sufficient.

• Victim interactionNot required

  No user interaction is needed; the fetcher sidecar processes the malicious archive autonomously once the resource is submitted.

• Attack complexityDetail

  Exploitation is reliable and condition-free: crafting a zip entry with a path-traversal sequence (e.g. ../../tmp/evil) and pointing a URL field at it is the only step required.

Blast Radius

• Writes arbitrary files into other tenants' /packages/<ns>/ directories on shared storage, corrupting or replacing their function packages.
• Overwrites files in mounted secret or ConfigMap volumes accessible to the fetcher sidecar, exposing or tampering with credentials and configuration data.
• Replaces the fetcher binary itself, enabling persistent code execution within the per-environment pod on the next fetcher invocation.
• No confidentiality impact is indicated by the CVSS vector; the attacker gains write capability but not direct read of protected data through this path alone.