{"id":"CVE-2026-46618","aliases":["GHSA-7pjr-qpvh-m339","GO-2026-5230"],"url":"https://o3.security/vulnerability/CVE-2026-46618","summary":"Fission builder accepts arbitrary buildcmd strings from Environment.spec.builder.command,   allowing the builder pod to invoke arbitrary executables","details":"### Summary\n\nBefore the round-1 security sweep, `pkg/builder/builder.go` passed `Environment.spec.builder.command` directly into `exec.Command(...)` after a `strings.Fields` split, with no validation of the executable path or its arguments. A user who could create or update `Environment` CRDs in a namespace observed by the buildermgr could thereby point the builder pod at any executable inside the builder image (e.g. `/bin/sh -c '...'`) and execute arbitrary code in the builder pod context.\n\n### Affected component\n\n- `pkg/builder/builder.go:254` — call site (`exec.Command(buildCmd, buildArgs...)`).\n- `pkg/builder/builder.go:106` — input source: `buildCmd, buildArgs = strings.Fields(req.BuildCommand)[0], strings.Fields(req.BuildCommand)[1:]`.\n\n### Impact\n\nA subject with `create` / `update` privilege on `Environment` objects could:\n\n1. Cause the builder pod for any package using that environment to execute arbitrary code.\n2. Read whatever files the builder pod has access to inside its `/packages` shared volume (deployment archive payloads for that package).\n3. Write arbitrary content into the `/packages` shared volume, which the fetcher subsequently uploads as the package deployment archive.\n\nThe builder pod runs in the user's namespace with the `fission-builder` SA (not the more-privileged executor SA), so the impact is bounded to that namespace's package contents and the builder pod's own filesystem. `PR:H` reflects that creating / modifying `Environment` CRDs is typically restricted to cluster admins or platform operators.\n\n### Root cause\n\n`pkg/builder/builder.go`'s build-command parser did not validate the resulting executable path. Although `exec.Command` does not invoke a shell, it does locate the executable via `$PATH`, and `strings.Fields` splitting allowed multiple flags / sub-arguments to be passed.\n\n### Fix\n\nReleased in [v1.23.0](https://github.com/fission/fission/releases/tag/v1.23.0):\n\n- **PR #3364** (commit `0f45c911`) introduces `Builder.resolveBuildCommand` in `pkg/builder/builder.go`, which:\n  1. Accepts an empty string (treated as the default `/build`).\n  2. Accepts the literal `/build`.\n  3. Accepts any absolute path that survives `filepath.Clean` and contains no `..` segments.\n  4. Rejects anything containing whitespace metacharacters or relative paths.\n- `exec.Command` still receives only the validated absolute path; sub-arguments continue to come from `strings.Fields` of the original string but are now passed positionally with no shell expansion.\n\n### Mitigation (until upgrade)\n\n1. Restrict who can create / update `Environment` CRDs to trusted operators only.\n2. Audit `Environment.spec.builder.command` values for any non-`/build` paths.\n3. Run the buildermgr with a tightened ServiceAccount that has no secret access in the builder namespace.","published":"2026-06-10T17:20:53.216Z","modified":"2026-08-12T03:51:08.161236575Z","cvss":null,"epss":{"score":0.00364,"percentile":0.29083,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/fission/fission","fixedVersion":"1.23.0"}],"fix":{"url":"https://github.com/fission/fission/pull/3364","label":"fission/fission#3364"},"references":[{"type":"WEB","url":"https://github.com/fission/fission/releases/tag/v1.23.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46618.json"},{"type":"ADVISORY","url":"https://github.com/fission/fission/security/advisories/GHSA-7pjr-qpvh-m339"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-46618"},{"type":"FIX","url":"https://github.com/fission/fission/pull/3364"},{"type":"PACKAGE","url":"https://github.com/fission/fission"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:08.161236575Z"}}