Langflow patched unauthenticated file upload in deprecated API endpoint
Langflow disclosed and fixed a vulnerability in the deprecated POST /api/v1/upload/{flow_id} endpoint that allowed unauthenticated users to upload arbitrary amounts of data without effective access control or flow validation. The flaw exposed affected servers to disk space exhaustion and denial-of-service, and the API response also revealed the absolute filesystem path of uploaded files. The issue was demonstrated against commit 2d67402 using any UUID as flow_id, showing that attackers could write data into a flow cache folder even without authorization.
The fix was merged through PR #12831 and released in Langflow 1.9.1, reusing the existing get_flow dependency to require authentication and verify flow ownership on the deprecated route. Maintainers also added file-size enforcement so oversized uploads now return HTTP 413, updated SDK helpers to support API-key authentication, and added regression tests covering unauthenticated rejection, authenticated uploads, oversized file handling, and 401 responses. After the patch, absolute file paths may still be returned, but only to the authenticated owner of the flow.
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2 events from the most recent confirmed update back to the earliest known activity.
GitHub advisory discloses Langflow upload DoS and path leak flaw
A GitHub security advisory disclosed that Langflow's deprecated upload endpoint allowed unauthenticated arbitrary data uploads, enabling disk space exhaustion and denial-of-service, while also leaking the absolute filesystem path of uploaded files in API responses. The advisory states the issue was fixed in Langflow version 1.9.1 through PR #12831.
Langflow merges auth fix for deprecated upload endpoint
Langflow merged PR #12831 into release-1.9.1 to secure the deprecated `/api/v1/upload/{flow_id}` endpoint by enforcing authentication and flow-ownership checks. The changes also added file size enforcement, SDK updates for API-key authentication, and regression tests.
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Langflow File Upload Flaw: PoC and DoS Details Public
securityonline.info
Open sourceUnauthenticated file upload leads to DoS (space exhaustion) and information leak · Advisory · langflow-ai/langflow · GitHub
github.com
Open sourcefix(security): require auth on deprecated /api/v1/upload/{flow_id} by erichare · Pull Request #12831 · langflow-ai/langflow · GitHub
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Langflow fixes IDOR letting authenticated users execute other users’ flows
Langflow disclosed a high-impact insecure direct object reference vulnerability, tracked as **`GHSA-qrpv-q767-xqq2`**, that allowed any authenticated user on affected deployments to access and execute another user’s flow through the **`/api/v1/responses`** endpoint. The flaw affected pip package versions earlier than **`1.9.1`** and stemmed from backend logic that resolved flows by UUID without verifying ownership, enabling an attacker to submit a victim’s flow UUID and receive the resulting output. Successful exploitation could expose sensitive data processed by the victim’s flow and consume the victim’s compute resources. The fix, merged in PR **`#12832`**, added ownership checks for both UUID- and endpoint-name-based flow lookups and changed unauthorized access handling to return **`404`** instead of **`403`** to avoid revealing whether a target flow exists. Langflow also hardened related routes, including **`/api/v1/run`**, **`/api/v1/run/session`**, and **`/api/v1/run/advanced`**, to close similar unscoped dependency patterns, and added regression tests covering cross-user access, malformed **`user_id`** inputs, and the reported proof of concept. Users are advised to upgrade to **`1.9.1`** or later.
Jun 20, 2026
Langflow Flaws Enable Cross-Tenant Access and Fuel Cryptominer Intrusions
Multiple vulnerabilities in **Langflow** have exposed AI application deployments to both account-to-account abuse and active compromise. **`CVE-2026-33760`** affects versions before **1.9.0** and allows authenticated users to read, modify, rename, or delete other users’ messages, sessions, build artifacts, and LLM transaction logs through seven `/api/v1/monitor` endpoints that fail to enforce ownership checks. A separate flaw, **`CVE-2026-55255`**, affects versions before **1.9.2** and lets an authenticated attacker execute another user’s flow through the `/api/v1/responses` endpoint by supplying a victim `flow_id`, giving the issue a critical **CVSS 9.9** rating. At the same time, defenders are tracking a cryptocurrency-mining campaign exploiting **`CVE-2026-33017`**, an unauthenticated remote code execution bug in Langflow, to compromise exposed instances and deploy Monero miners. Threat research says the malware disables security controls, installs persistence, and can enable lateral movement through reused SSH keys; observed infrastructure includes **`83.142.209.214`** and **`94.156.64.241`**. Organizations running Langflow are being urged to upgrade to **1.9.0** and **1.9.2** or later as applicable, verify access-control enforcement, restrict public exposure of Langflow services, and treat signs of miner activity or unauthorized flow execution as a significant incident.
Jun 24, 2026
Actively Exploited Langflow RCE Exposed AI Pipeline Secrets and Triggered CISA KEV Listing
Threat actors rapidly exploited **CVE-2026-33017**, a critical unauthenticated remote code execution flaw in Langflow’s public flow build endpoint, allowing arbitrary Python code to reach an unsandboxed `exec()` path with a single crafted request. The bug affects Langflow versions prior to **1.9.0** and stems from the `POST /api/v1/build_public_tmp/{flow_id}/flow` endpoint accepting attacker-controlled flow data through an optional parameter. Researchers and vendor advisories said the issue is distinct from **CVE-2025-3248** because the vulnerable endpoint is intentionally public, meaning the fix required removing attacker-supplied flow data from that execution path rather than simply adding authentication. Sysdig and other researchers reported exploitation beginning within about **20 hours** of disclosure, with attackers scanning for exposed instances, validating code execution, reading files such as `.env`, `.db`, and `/etc/passwd`, stealing credentials, API keys, and database secrets, and attempting follow-on payload delivery from infrastructure including `173.212.205[.]251:8443`. The severity prompted **CISA** to add the flaw to its **Known Exploited Vulnerabilities** catalog and order federal agencies to remediate by **April 8, 2026** or discontinue use if they could not secure affected systems. Security guidance across the reports urged organizations to upgrade to **Langflow 1.9.0 or later**, restrict or remove internet exposure of the vulnerable endpoint, monitor outbound connections, and rotate secrets if compromise is suspected.
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