CVE-2026-55446 Langflow: Unauthenticated DoS through multipart form boundary file upload
Unauthenticated attackers can cause indefinite denial of service in Langflow by sending requests with excessively long multipart form boundaries.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55446?
CVE-2026-55446 is a high-severity denial of service vulnerability in Langflow Langflow, published on 23 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.0.19, an attacker can send a /api/v1/files/upload/ request without any authentication token/cookies and abuse a very long multipart form boundary to make the langflow app unusable for all users for an indefinite amount of time. This vulnerability is fixed in 1.0.19.
Weakness: CWE-400
Which versions are affected by CVE-2026-55446?
3 open source packages ship an affected version, including langflow. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
langflow PyPI | All versions | 1.0.19 |
langflow PyPI | All versions | 1.0.19 |
langflow PyPI | All versions | 1.0.19 |
Products include Langflow Langflow.
How do I fix CVE-2026-55446?
Upgrade langflow to 1.0.19 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-55446 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55446 exists.
Other vulnerabilities in Langflow Langflow
Sources
Also known as GHSA-qwqc-p3q8-wcg9, PYSEC-2026-223.