CVE-2026-100681 in Budibase
Summary
by MITRE • 09/26/2026
Budibase before 3.45.0 contains an unauthenticated server-side request forgery and credential exfiltration vulnerability in the Microsoft Teams webhook endpoint that accepts forged Bot Framework activities with arbitrary serviceUrl values. Attackers can submit a crafted POST request to inject an attacker-controlled serviceUrl that is persisted and used for all subsequent bot replies, causing the server to send live Microsoft OAuth access tokens in Authorization headers to the attacker's host and enabling blind internal network access.
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Analysis
by VulDB Data Team • 09/26/2026
The vulnerability identified in Budibase versions prior to 3.45.0 represents a critical security flaw within its integration with Microsoft Teams via the Bot Framework API. This issue manifests as an unauthenticated server-side request forgery combined with credential exfiltration, specifically targeting the webhook endpoint responsible for handling incoming bot activities. The core technical failure lies in the application's insufficient validation of the serviceUrl field contained within POST requests that simulate legitimate Bot Framework activity payloads. By accepting arbitrary values for this parameter without rigorous verification against a whitelist or expected domain patterns, the system allows an attacker to inject their own controlled URL into the configuration used by the server for subsequent communications.
When an attacker submits a crafted HTTP POST request containing a malicious serviceUrl, Budibase persists this value as part of its internal state management for that specific bot instance. This persistence mechanism is critical because it dictates where all future replies and notifications from the application are directed. Consequently, any action triggered by the system that results in a message being sent to Microsoft Teams will instead route that traffic through the attacker-controlled endpoint. This architectural oversight transforms what might appear as a simple configuration error into a powerful vector for data theft and internal network reconnaissance, leveraging the trusted relationship between Budibase and the Microsoft 365 ecosystem.
The operational impact of this vulnerability is severe due to the nature of OAuth2 authentication flows within Microsoft Teams. When the server attempts to send messages or perform actions on behalf of users or service accounts, it attaches a live Microsoft OAuth access token in the Authorization header of outgoing requests. Because these requests are now directed to the attacker's host rather than the legitimate Microsoft Teams infrastructure, the attacker gains direct access to these sensitive tokens. These tokens typically possess broad permissions depending on the scope granted during initial authentication, potentially allowing the adversary to impersonate users, read private messages, modify team data, or access other connected services linked to those accounts without further authentication challenges.
Beyond immediate credential theft, this vulnerability facilitates blind internal network access and lateral movement within an organization's digital environment. The ability to exfiltrate tokens enables attackers to pivot into deeper layers of the Microsoft 365 suite, including SharePoint, OneDrive, or Azure AD resources associated with compromised identities. Furthermore, if the Budibase instance has integrations with other internal systems that rely on similar token-based authentication patterns exposed through this webhook mechanism, those connections may also be exploited. The lack of input validation allows for potential amplification attacks where the forged requests could trigger actions in downstream services, effectively turning the application into a proxy for unauthorized access to protected resources.
From a classification perspective, this flaw aligns with CWE-918 Server-Side Request Forgery (SSRF), as it involves manipulating server-side logic to make requests on behalf of the user or system to an unintended destination. It also relates closely to CWE-200 Exposure of Sensitive Information to an Unauthorized Actor and CWE-798 Use of Hard-coded Credentials if any static keys were involved, though here the primary issue is the dynamic exfiltration of session tokens. In terms of MITRE ATT&CK mapping, this activity corresponds to T1556 Modifying Authentication Process for Credential Access or T1048 Exfiltration Over Alternative Protocol, as the attacker uses standard HTTP protocols but redirects them to malicious infrastructure to steal authentication material.
Mitigation strategies must focus on immediate remediation and long-term architectural improvements. The primary defense is upgrading Budibase to version 3.45.0 or later, where this validation logic has been corrected to ensure that serviceUrl values are strictly validated against expected Microsoft Teams domains. For organizations unable to upgrade immediately, implementing a Web Application Firewall rule to inspect POST requests targeting the Bot Framework webhook endpoint can provide temporary relief by blocking payloads with non-Microsoft URLs in the serviceUrl field. Additionally, enforcing strict CORS policies and ensuring that API endpoints require authentication even for initial configuration steps would reduce the attack surface. Regular auditing of integration configurations and monitoring logs for unusual outbound traffic patterns to unknown external hosts are also recommended practices to detect potential exploitation attempts early.