CVE-2026-18545 in Langflow OSS
Summary
by MITRE • 08/29/2026
IBM Langflow OSS 1.0.0 through 1.11.1 is vulnerable to server-side request forgery (SSRF). This may allow an authenticated attacker to send unauthorized requests from the system, potentially leading to network enumeration or facilitating other attacks.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 08/29/2026
The vulnerability identified in IBM Langflow versions 1.0.0 through 1.11.1 represents a critical server-side request forgery flaw that compromises the integrity of authenticated interactions with external services. Server-side request forgery, commonly referred to as SSRF, occurs when an application retrieves data from a remote resource specified by the user without performing adequate validation on the destination address or protocol. In this specific instance, the vulnerability stems from insufficient sanitization and verification mechanisms within the Langflow framework's handling of URLs provided during authenticated sessions. This allows an attacker who has successfully obtained valid credentials to manipulate input fields that are subsequently used to construct HTTP requests by the server itself. The core technical flaw lies in the application's failure to restrict outbound connections to a predefined whitelist of trusted domains or IP ranges, thereby granting the authenticated user significant control over where the backend system directs its network traffic.
From an operational perspective, this vulnerability poses severe risks beyond simple unauthorized access. Because the requests originate from the server itself, they bypass many perimeter security controls such as firewalls and intrusion detection systems that typically filter inbound traffic but may not inspect outbound traffic with equal rigor. An attacker can leverage this capability to perform internal network enumeration by probing private IP addresses on common ports, effectively mapping out the internal infrastructure behind the firewall. This reconnaissance activity is often a precursor to more destructive attacks, such as accessing sensitive internal services like database management interfaces, cloud metadata endpoints, or administrative consoles that are not exposed to the public internet but remain accessible from within the network segment where Langflow resides. The ability to interact with these hidden resources can lead to data exfiltration, lateral movement across the network, and potentially full system compromise if combined with other vulnerabilities in internal services.
The classification of this issue aligns closely with CWE-918, which defines Server-Side Request Forgery as a weakness where an application retrieves a remote resource without validating user-supplied URL information. Furthermore, from a tactical standpoint, the exploitation technique maps to MITRE ATT&CK techniques related to Network Service Discovery and potentially Cloud Metadata API queries if deployed in cloud environments. The presence of authentication requirements does not mitigate the severity because many enterprise deployments utilize service accounts or automated workflows that maintain persistent authenticated sessions, making them prime targets for such abuse. Once an attacker gains a foothold through valid credentials, which may be obtained via phishing, credential stuffing, or other means, this SSRF vulnerability serves as a powerful pivot point to expand their access within the organization's digital estate.
Mitigation strategies must focus on implementing strict egress filtering and input validation at multiple layers of the infrastructure. The most effective immediate remediation is to upgrade IBM Langflow to version 1.12 or later, where this specific vulnerability has been addressed by developers through improved URL parsing logic and stricter allow-listing policies for outbound connections. In environments where upgrading is not immediately feasible, network-level controls should be enforced. This includes configuring firewalls to restrict the server's ability to initiate connections to private IP address ranges such as 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, which are commonly targeted in SSRF attacks for internal enumeration. Additionally, implementing a web application firewall with rules that detect and block requests containing suspicious patterns or non-standard ports can provide an additional layer of defense. It is also critical to ensure that the principle of least privilege is applied to service accounts used by Langflow, limiting their permissions so that even if SSRF occurs, the impact on internal resources remains contained. Regular auditing of outbound network logs and monitoring for anomalous connection patterns originating from application servers can further aid in early detection and response to potential exploitation attempts.