{"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":0.00231,"epssPercentile":0.14177,"ingestedAt":"2026-06-30T21:24:14.415Z","slug":"CVE-2026-49821","body":"## Overview\n\n### Summary\n\nFission's `buildermgr` controller processed `Package` CRDs without verifying that `Package.spec.environment.namespace` matched `Package.metadata.namespace`.\n\n### Details\n\nAn 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\ncross-namespace and dispatch the build command into the **victim namespace's** builder pod.\n\nThe 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\n`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.\n\n### Impact\n\nCross-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\n the victim namespace.\n\n### Fix\n\nFixed 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:\n\n- **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.\n- **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\nwebhook-bypass cluster (`failurePolicy=Ignore`) cannot exploit the primitive either.\n\n### Behavioural change\n\nPackages 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).\n\n## Affected packages\n\n- `github.com/fission/fission <= 1.23.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `github.com/fission/fission 1.24.0`","depth":"twilight","depthScore":42,"depthScoreParts":{"impact":42.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}