Langflow: unauthenticated code execution in the validation API (CVE-2025-3248)

An unauthenticated caller can submit Python to the affected Langflow code-validation endpoint and execute it with the service’s privileges. Update Langflow to remove remote access to that execution path.

Public CVE record · Native module source

CVE advisory record · Vendor advisory · Module source

Result. The marked request reached the backend in the baseline and raised its counter. The native rule refused that request with HTTP 403 and preserved HTTP 200 for the benign probe. The synthetic fixture ran through Eden 1.103.0 on November 12, 2026 (UTC).

The vulnerability

Langflow’s code-validation endpoint accepted unauthenticated input that could reach Python execution. A service account’s filesystem and network permissions determine what arbitrary Python execution can reach. This endpoint is especially sensitive when reachable beyond the operators who build flows.

Langflow 1.3.0 contains the fix. The CVE record reports a CVSS base score of 9.8.

The Eden patch

Tier 1 — declarative policy. The recorded policy denies requests to /api/v1/validate/code and its descendants. The empty method list leaves the deny unrestricted by HTTP method. This is a coarse rule and blocked the benign probe on the same path.

{
  "version": 1,
  "profile": "http-structure-v1",
  "policy": {
    "version": 1,
    "rules": [
      {
        "scope": {
          "methods": [],
          "path": "/api/v1/validate/code",
          "descendants": true
        },
        "require": {
          "kind": "deny"
        }
      }
    ]
  }
}

Tier 2 — native Rust module. gabriel_langflowrce_v1 waits for the request to be complete, checks whether the request target starts with /api/v1/validate/code, and looks for any configured marker in the body. The substring comparison is ASCII case-insensitive. Outside that prefix or without a marker, the module returns Continue. The shown lines are excerpts from the linked source.

const ROUTE: &[u8] = b"/api/v1/validate/code";
static NEEDLES: [&[u8]; 4] = [b"exec(", b"eval(", b"system(", b"subprocess"];

NEEDLES.iter().any(|n| find_ignore_case(body, n).is_some()) && return Ok(Decision::Refuse);

Implement the remediation

The commands are operator examples for the recorded scope. Compare fixture routes and software selectors with the intended deployment before use. See deployment prerequisites.

1. Prepare the target. Verify the loaded product and version against the advisory. Use a compatible Eden HTTP interlay and an authenticated operator with Configure permission. Use the recorded declaration and the linked source when applicable.
2. Apply the declarative policy. Scope the policy to /api/v1/validate/code and descendants (all methods, deny). Set INTERLAY to the target interlay UUID in the authenticated Eden CLI. Run an authenticated GET /api/v1/interlays/{interlay} with X-Eden-Verbose: true. Save its complete current settings object as current-settings.json and retain the prior remediation declaration for recovery. Set IDEMPOTENCY_KEY to a fresh key for this intended mutation.

Save the JSON in the patch section as remediation.json.

jq -e --slurpfile policy remediation.json \
  '.remediation = $policy[0] | {settings: .}' current-settings.json \
  > interlay-update.json
eden api request PATCH "/api/v1/interlays/$INTERLAY" \
  --header "Idempotency-Key:$IDEMPOTENCY_KEY" \
  --body-file interlay-update.json --content-type application/json --confirm

3. Verify the serving policy. Read back the interlay.

eden api request GET "/api/v1/interlays/$INTERLAY" \
  --header 'X-Eden-Verbose:true'

Check that remediation_status.state is ready and both desired and effective SHA-256 values match the intended declaration. Replay the benign and marked requests in the recorded comparison on an isolated target. Check the recorded response and backend outcome for each probe. 4. Restore the previous policy. Coordinate the change with any other operator updating this interlay. Read current settings again and merge the saved remediation field into them. If the prior settings had no remediation field, omit it in the replacement. Send the same PATCH with a fresh idempotency key, then read back the intended state. Repeat the verification probes. Keep the affected route isolated if restoring the prior settings reopens exposure.

Native module gabriel_langflowrce_v1

1. Prepare the archive. Use the linked source and a compatible Eden SDK. Obtain the built archive and manifest from a qualified Eden build environment. Configure independent host approval for the installed Eden release. Use the authenticated principals required by the native authority contract. Set PATCH_ARCHIVE to the exact schema-2 package and PACKAGE_SHA256 to its expected archive digest. Verify and import it using the same target interlay.

printf '%s  %s\n' "$PACKAGE_SHA256" "$PATCH_ARCHIVE" | sha256sum --check &&
  eden api request PUT "/api/v1/interlays/$INTERLAY/patch-packages/$PACKAGE_SHA256" \
    --body-file "$PATCH_ARCHIVE" \
    --content-type application/vnd.eden.patch-package.v2+tar --confirm

2. Approve and activate. Enroll the publisher key, attest host software inventory, and inspect the configuration returned by import. Obtain independent host approval. Sign the typed statement with the matching SDK. Send the admit action followed by activate for the prepared operation. Use the applicable typed payload for each action in authority-action.json.

eden api request POST "/api/v1/interlays/$INTERLAY/native-authority" \
  --body-file authority-action.json --content-type application/json --confirm

3. Verify the operation. Read the receipt through the same endpoint. Confirm serving_now and the full expected shard acknowledgment. Repeat the report’s benign and marked probes and check the backend observations.
4. Revoke or restore. Send revoke with the exact operation UUID. Mandatory protection can refuse traffic until a compatible operation is approved and activated. Verify the restored receipt and repeat the probes.

Vendor update. Use the advisory and its product-specific vendor references to select the fixed release for the exact installed product or package and release line. Follow its update instructions and confirm the version actually loaded by the service.

Fixture and probes

The fixture was a synthetic HTTP handler behind Eden. It answered the probes and kept a separate counter that increased when the handler recognized its marker bytes. The counter measures a fixture effect. An HTTP 200 from the baseline does not by itself establish that the counter moved.

Request. POST /api/v1/validate/code for the benign probe and the marked probe.

The benign request supplied a simple print expression. The second contained an execution call. The backend incremented a marker after matching the raw body. The fixture ran no Python supplied by either request.

Measured comparison (2026-11-12 UTC)

The values after each status are the observed increases in the backend marker counter.

Signed module authority

The module import returned HTTP 201 and required explicit activation. Signature verification was deferred at import. Read-only inspection returned HTTP 403, admission with a tampered statement returned HTTP 400, and admission with an invalid signature returned HTTP 403. The activation receipt reported the module serving on all expected shards.

After revocation, the same marked request received HTTP 503. Re-approval and reactivation restored HTTP 403. The source digest below identifies the linked Rust file. The binary digest identifies the artifact recorded in the activation evidence.

• Source SHA-256 9e517ac5c21023247dc58456b6f198dfd5ab182ea8c912029ef0d9dacac77536
• Tested binary SHA-256 83e3952b2adba2b7a09e70c4d9f2cd8534c0bccb40794195b33381cc05fc34db

Test scope

The synthetic route matches the advisory endpoint. The rule is a substring check, so even a comment or string mentioning one of these names can trigger it. Alternate Python constructs or encodings that lack those bytes remain unverified.

Performance

The public evidence for this case does not include request-latency measurements.

Evidence and artifacts

• Public CVE record
• Published module source