GHSA-7PJR-QPVH-M339

Vulnerability from github – Published: 2026-05-21 20:17 – Updated: 2026-06-10 18:42
VLAI
Summary
Fission builder accepts arbitrary buildcmd strings from Environment.spec.builder.command, allowing the builder pod to invoke arbitrary executables
Details

Summary

Before 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.

Affected component

  • pkg/builder/builder.go:254 — call site (exec.Command(buildCmd, buildArgs...)).
  • pkg/builder/builder.go:106 — input source: buildCmd, buildArgs = strings.Fields(req.BuildCommand)[0], strings.Fields(req.BuildCommand)[1:].

Impact

A subject with create / update privilege on Environment objects could:

  1. Cause the builder pod for any package using that environment to execute arbitrary code.
  2. Read whatever files the builder pod has access to inside its /packages shared volume (deployment archive payloads for that package).
  3. Write arbitrary content into the /packages shared volume, which the fetcher subsequently uploads as the package deployment archive.

The 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.

Root cause

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.

Fix

Released in v1.23.0:

  • PR #3364 (commit 0f45c911) introduces Builder.resolveBuildCommand in pkg/builder/builder.go, which:
  • Accepts an empty string (treated as the default /build).
  • Accepts the literal /build.
  • Accepts any absolute path that survives filepath.Clean and contains no .. segments.
  • Rejects anything containing whitespace metacharacters or relative paths.
  • 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.

Mitigation (until upgrade)

  1. Restrict who can create / update Environment CRDs to trusted operators only.
  2. Audit Environment.spec.builder.command values for any non-/build paths.
  3. Run the buildermgr with a tightened ServiceAccount that has no secret access in the builder namespace.
Severity
6.9 (Medium)
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
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.22.0"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/fission/fission"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.23.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-46618"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-250",
      "CWE-269",
      "CWE-78"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-21T20:17:24Z",
    "nvd_published_at": "2026-06-10T18:17:05Z",
    "severity": "MODERATE"
  },
  "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 \u0027...\u0027`) and execute arbitrary code in the builder pod context.\n\n### Affected component\n\n- `pkg/builder/builder.go:254` \u2014 call site (`exec.Command(buildCmd, buildArgs...)`).\n- `pkg/builder/builder.go:106` \u2014 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\u0027s namespace with the `fission-builder` SA (not the more-privileged executor SA), so the impact is bounded to that namespace\u0027s package contents and the builder pod\u0027s 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`\u0027s 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.",
  "id": "GHSA-7pjr-qpvh-m339",
  "modified": "2026-06-10T18:42:10Z",
  "published": "2026-05-21T20:17:24Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Fission builder accepts arbitrary buildcmd strings from Environment.spec.builder.command, allowing the builder pod to invoke arbitrary executables"
}



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