{"id":"CVE-2026-49821","aliases":["GHSA-vjhc-cf4p-72q4","GO-2026-5859"],"url":"https://o3.security/vulnerability/CVE-2026-49821","summary":"Fission: Cross-namespace Environment reference in Package allows build-time command execution and SA token exfiltration","details":"### 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).","published":"2026-06-10T17:21:48.470Z","modified":"2026-08-12T03:51:41.099228567Z","cvss":{"score":7.7,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N"},"epss":{"score":0.00231,"percentile":0.14114,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/fission/fission","fixedVersion":"1.24.0"}],"fix":{"url":"https://github.com/fission/fission/pull/3379","label":"fission/fission#3379"},"references":[{"type":"WEB","url":"https://github.com/fission/fission/releases/tag/v1.24.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49821.json"},{"type":"ADVISORY","url":"https://github.com/fission/fission/security/advisories/GHSA-vjhc-cf4p-72q4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49821"},{"type":"FIX","url":"https://github.com/fission/fission/pull/3379"},{"type":"WEB","url":"https://github.com/fission/fission/commit/e2b92663499f4dc3a1e2d38178f39c3c65e0134a"},{"type":"PACKAGE","url":"https://github.com/fission/fission"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:41.099228567Z"}}