CVE-2026-46618: Github.com/fission/fission Fission Builder Accepts Arbitrary Buildcmd Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7pjr-qpvh-m339",
  "modified" : "2026-06-10T18:42:10Z",
  "published" : "2026-05-21T20:17:24Z",
  "aliases" : [ "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.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/fission/fission"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.23.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.22.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "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" : "WEB",
    "url" : "https://github.com/fission/fission/pull/3364"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/fission/fission"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/fission/fission/releases/tag/v1.23.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-250", "CWE-269", "CWE-78" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-21T20:17:24Z",
    "nvd_published_at" : "2026-06-10T18:17:05Z"
  }
}