Unauthenticated Remote Code Execution in Langflow via Public Flow Build Endpoint

Exploitation

Confirmed: listed in the CISA Known Exploited Vulnerabilities catalog.

CVSS 4.0

9.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/E:A · score source

EPSS

• CVE-2026-33017: 96.18% estimated exploitation activity in the next 30 days; percentile 99.88 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The POST /api/v1/buildpublictmp/{flowid}/flow endpoint allows building public flows without requiring authentication. When the optional data parameter is supplied, the endpoint uses attacker-controlled flow data (containing arbitrary Python code in node definitions) instead of the stored flow data from the database. This code is passed to exec() with zero sandboxing, resulting in unauthenticated remote code execution. This is distinct from CVE-2025-3248, which fixed /api/v1/validate/code by adding authentication. The buildpublictmp endpoint is designed to be unauthenticated (for public flows) but incorrectly accepts attacker-supplied flow data containing arbitrary executable code. Affected Code Vulnerable Endpoint (No Authentication) File: src/backend/base/langflow/api/v1/chat.py, lines 580-657 Compare with the authenticated build endpoint at line 138, which requires currentuser: CurrentActiveUser. Code Execution Chain When attacker-supplied data is provided, it flows…

Published by the source

17 Mar 2026, 20:05 UTC

Last modified by the source

29 Jun 2026, 12:26 UTC

Source last checked

26 Oct 2026, 13:45 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vwmf-pq79-vjvx

2. Revision 3 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-vwmf-pq79-vjvx

4. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-vwmf-pq79-vjvx

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# Patch Next advisory brief: CVE-2026-33017

Advisory: Unauthenticated Remote Code Execution in Langflow via Public Flow Build Endpoint
IDs: CVE-2026-33017, GHSA-vwmf-pq79-vjvx
Record: https://patchnext.com/advisories/cve-2026-33017 (revision 4, source checked 26 Oct 2026, 13:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: confirmed: listed in the CISA Known Exploited Vulnerabilities catalog.
Vendor response: Vendor fix available; fixed versions by package: langflow 1.9.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI langflow: affected <= 1.8.2; fixed in 1.9.0

## Suggested inspection (read-only)
- `python -m pip show langflow`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on langflow.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-vwmf-pq79-vjvx (GitHub-reviewed advisory GHSA-vwmf-pq79-vjvx lists affected ranges: PyPI langflow >=0 <=1.8.2)
- Verified: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CISA added CVE-2026-33017 to the Known Exploited Vulnerabilities catalog on 2026-03-25.)
- Verified: https://osv.dev/vulnerability/GHSA-vwmf-pq79-vjvx (OSV record GHSA-vwmf-pq79-vjvx lists affected ranges: PyPI langflow >=0 <1.9.0 (fixed))

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