CVE-2026-55255: Langflow Authorization Bypass Through User-Controlled Key Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Langflow Langflow. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-07-07, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-07-10; treat that as the outer limit, not the target.
• EPSS 0.9%, percentile 59: FIRST’s model estimates a 0.9% chance of exploitation activity in the next 30 days, higher than 59% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Editorial verdict: Act now. Langflow CVE-2026-9198: Exploited Unauthenticated RCE — Langflow is now the most repeatedly exploited AI-agent builder on CISA's list; any network-reachable instance below 1.10.1 should be patched today and checked for compromise.

What it is

Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.1, an Insecure Direct Object Reference (IDOR) vulnerability in /api/v1/responses endpoint allows an authenticated attacker to execute any flow belonging to another user by specifying the victim's flow ID in the request. This vulnerability is fixed in 1.9.1.

CISA’s summary

Langflow contains an authorization bypass through user-controlled key vulnerability which allows an authenticated attacker to execute any flow belonging to another user by specifying the victim's flow ID in the request.

Weakness type: CWE-639.

Product: Langflow Langflow · Assigned by: GitHub_M · Published: 2026-06-23

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: high (needs special conditions)
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2026-07-07; federal due date 2026-07-10. Known ransomware use: Unknown.
• CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
• CISA SSVC assessment: exploitation active, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.89% probability of exploitation activity in the next 30 days; percentile 59.

Timeline

• 2026-06-23 — CVE record published by GitHub_M
• 2026-07-07 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2026-07-10 — CISA remediation deadline for US federal agencies
• 2026-08-04 — erroneo.us brief: Langflow CVE-2026-9198: Exploited Unauthenticated RCE
• 2026-10-07 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (github.com) github.com

Vulnerability records

1. CVE.org record CVE-2026-55255 cve.org
2. NVD entry CVE-2026-55255 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov
2. Listed in CISA KEV notes (cisa.gov) cisa.gov
3. Listed in CISA KEV notes (cisa.gov) cisa.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. webflow.sysdig.com webflow.sysdig.com

All exploited Langflow vulnerabilities · Today’s Security Digest