Vulnerability report

Active exploitation observed Confirmed confidence Not in CISA KEV

CVE-2026-55450

langflow Denial of Service

Langflow-ai / langflow · affected before 1.9.1

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Severity
CVSS 9.3 · Critical
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
1.2%
First observed
08 Aug 2026
Last observed
12 Sep 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2026-55450 is an unauthenticated vulnerability affecting Langflow-ai langflow. Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.1, unauthenticated users can upload any...

Is it exploited?

Yes. Previdian sensors observed exploitation attempts with confirmed confidence.

Who is affected?

Langflow-ai / langflow affected before 1.9.1.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

Langflow is a tool for building and deploying AI-powered agents and workflows

Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.1, unauthenticated users can upload any amount of data to the server without any limitations. No need for any prior knowledge, only network access to Langflow.

This can lead to space exhaustion on the server. In addition, in the response, the absolute path of the uploaded file is reported to the attacker, which is an information leak that can assist in chaining other primitives. This vulnerability is fixed in 1.9.1.

Vendor Product Affected Status
langflow-ai langflow Before 1.9.1 Affected
Published
23 Jun 2026
Exploitation Reported
08 Aug 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

nuclei_scanner

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

Previdian

Recorded 08 Aug 2026

Previdian independently recorded this as exploited after first seeing it in honeypot sensors.

Active exploitation observed

Previdian sensor

First observed 08 Aug 2026

Previdian first observed exploitation attempts targeting this vulnerability in our honeypot sensors.

Proof of concept available

Nuclei Templates

Recorded 01 Aug 2026

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

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Source Added
Previdian First 2026-08-09 12:09 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

First-party evidence of exploitation activity

Previdian sensors recorded exploitation attempts targeting this vulnerability. The cards and chart show volume, unique attackers, and daily activity.

16

Attempts observed

13

Unique attacker IPs

7

Attacker countries

CA · ER · HK · MD · MY · SG · US

7

Sensors observed

CVE-2026-55450 exploitation attempts over the last 38 days

Daily events observed by Previdian sensors

Updated 13 Sep 2026

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1
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0
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7 Aug 15 Aug 23 Aug 31 Aug 13 Sep

First observed 08 Aug 2026 · Last observed 12 Sep 2026

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Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
2
14
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

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Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

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Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-55450.yaml 01 Aug 2026

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.3 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:H

EPSS

1.2%

Weaknesses

Exposure of Sensitive Information to an Unauthorized Actor CWE-200 Missing Authentication for Critical Function CWE-306 Uncontrolled Resource Consumption CWE-400

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

Langflow < 1.9.1 - Unauthenticated File Upload

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. Indicators of compromise added (16)

    Indicators of compromise recorded

  2. Observed by Previdian sensors

    Evidence-backed exploitation signal

  3. Public PoC available

    Public proof-of-concept code published

  4. Nuclei template available

    Scanner coverage available

  5. CVE published

    Vulnerability disclosed publicly

  6. CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2026-55450

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2026-55450",
  "confidence": "Confirmed",
  "cvss_score": 9.3,
  "cvss_estimated": false,
  "epss_score": 0.0119,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 16, "sensors": 7 }
}