CVE-2026-19304: Langflow Information Disclosure Vulnerability

CVE-2026-19304 Overview

CVE-2026-19304 is a Server-Side Request Forgery (SSRF) vulnerability in IBM Langflow OSS versions 1.0.0 through 1.11.2. The flaw stems from a URL parser discrepancy that allows a remote authenticated attacker to coerce the Langflow server into issuing requests to internal services. Successful exploitation exposes sensitive information reachable from the application's network position, including internal APIs, metadata endpoints, and other resources not intended for external access. The vulnerability is tracked under CWE-918 and affects Langflow deployments on macOS, Linux, and Windows hosts.

Critical Impact
An authenticated attacker can bypass network segmentation controls and read confidential data from internal services adjacent to the Langflow instance.

Affected Products

IBM Langflow OSS versions 1.0.0 through 1.11.2
Deployments on Apple macOS, Linux kernel-based distributions, and Microsoft Windows
Any downstream integrations that trust Langflow's outbound network requests

Discovery Timeline

2026-09-04 - CVE-2026-19304 published to NVD
2026-09-08 - Last updated in NVD database

Technical Details for CVE-2026-19304

Vulnerability Analysis

The vulnerability is a Server-Side Request Forgery weakness rooted in inconsistent URL parsing between validation and request-execution components of Langflow. When Langflow accepts a URL from an authenticated user, one parser evaluates the input for host allow-list or block-list decisions. A different parser then dispatches the outbound HTTP request. Discrepancies between these two parsers let an attacker craft a URL that appears benign to the validator but resolves to an internal destination when the HTTP client executes it. The attacker abuses this gap to reach internal-only services from the Langflow process context.

The attack requires low privileges and no user interaction, and the scope is changed because the vulnerable component pivots requests into resources beyond its own security boundary. Impact is limited to confidentiality: the server returns responses from internal services back to the authenticated caller, disclosing configuration data, cloud metadata, or other adjacent service content.

Root Cause

The root cause is a parser mismatch, a class of SSRF defect where two libraries interpret the same URL string differently. Techniques such as embedding userinfo segments, using unusual host encodings, exploiting IPv6 zone identifiers, or leveraging punycode can cause the validation parser to see one host while the network client contacts another. Langflow's URL-fetching workflows do not enforce a single canonical parsed representation before both the security check and the outbound request.

Attack Vector

An authenticated attacker submits a crafted URL through a Langflow component that performs server-side HTTP requests. The application accepts the URL because its validator resolves it to an external host, then issues a request that instead reaches an internal target such as 169.254.169.254, localhost, or an RFC1918 address. Responses returning cloud instance metadata, internal admin endpoints, or private service data are relayed back to the attacker. No exploit code has been published, and CVE-2026-19304 is not listed in the CISA Known Exploited Vulnerabilities catalog.

No verified public exploit code is available for CVE-2026-19304. See the IBM Support Document for authoritative technical details.

Detection Methods for CVE-2026-19304

Indicators of Compromise

Outbound HTTP requests from the Langflow process to internal RFC1918 ranges, 127.0.0.0/8, or cloud metadata endpoints such as 169.254.169.254
Langflow application logs showing user-submitted URLs that contain unusual encodings, embedded credentials, or mixed-format hostnames
Unexpected authenticated API calls to Langflow components that accept URL parameters, followed by large response payloads

Detection Strategies

Correlate authenticated Langflow session activity with outbound network flows to detect requests targeting internal address space
Alert on any DNS resolution requests made by the Langflow service for hostnames that resolve to private or loopback addresses
Inspect Langflow audit trails for URL inputs that fail canonicalization checks or contain characters commonly abused in parser-confusion attacks

Monitoring Recommendations

Ingest Langflow application and reverse-proxy logs into a centralized analytics platform for correlation with network telemetry
Baseline normal outbound destinations for the Langflow service and alert on deviations, especially toward metadata or management endpoints
Monitor cloud instance metadata service (IMDS) access counters and enforce IMDSv2 session tokens where available

How to Mitigate CVE-2026-19304

Immediate Actions Required

Upgrade IBM Langflow OSS to a fixed release as documented in the IBM Support Document
Restrict outbound network access from the Langflow host to only the destinations required for legitimate workflows
Require IMDSv2 on cloud instances hosting Langflow to prevent trivial metadata theft via SSRF
Review authentication logs and revoke sessions or API keys used to exercise URL-fetching components since the vulnerability was disclosed

Patch Information

IBM has published remediation guidance for CVE-2026-19304 in the IBM Support Document. Administrators should upgrade past Langflow OSS 1.11.2 to the fixed version referenced in the advisory. Verify the deployed version with pip show langflow or the equivalent package manager query after patching.

Workarounds

Place Langflow behind an egress proxy that enforces a strict allow-list of external hostnames and blocks private, loopback, and link-local ranges
Deploy network policies or security groups that deny traffic from the Langflow workload to 169.254.169.254, 127.0.0.0/8, and internal management subnets
Limit access to authenticated Langflow accounts through single sign-on and enforce least-privilege roles until patching is complete

bash

# Example egress restriction using iptables to block IMDS and loopback pivoting
iptables -A OUTPUT -m owner --uid-owner langflow -d 169.254.169.254 -j REJECT
iptables -A OUTPUT -m owner --uid-owner langflow -d 127.0.0.0/8 ! -o lo -j REJECT
iptables -A OUTPUT -m owner --uid-owner langflow -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner langflow -d 172.16.0.0/12 -j REJECT
iptables -A OUTPUT -m owner --uid-owner langflow -d 192.168.0.0/16 -j REJECT