CVE-2026-85667 in xiaobei
Summary
by MITRE • 09/04/2026
xiaobei through 5.5.2 fails to implement authentication or signature validation on webhook endpoints, allowing unauthenticated attackers to inject arbitrary messages into the agent pipeline. Attackers can publish malicious messages via the /webhook_worktool handler and exploit unvalidated media URL fetching to perform server-side request forgery against internal services.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified in xiaobei versions through 5.5.2 represents a critical failure in input validation and access control mechanisms within its webhook processing subsystem. Specifically, the application fails to implement authentication or signature verification on endpoints designed to receive external data payloads, most notably the /webhook_worktool handler. This architectural oversight allows unauthenticated actors to interact directly with internal service logic without providing valid credentials or cryptographic proof of message integrity. In modern secure software design, webhook endpoints must enforce strict identity verification and ensure that incoming requests originate from trusted sources using mechanisms such as HMAC signatures or OAuth tokens. The absence of these controls transforms the endpoint into an open channel for malicious actors to inject arbitrary data directly into the agent pipeline, bypassing any intended security boundaries.
The operational impact of this flaw is severe due to the nature of the injected payloads and their downstream effects. Attackers can exploit the unvalidated media URL fetching functionality associated with these webhooks to perform Server-Side Request Forgery attacks against internal services. By supplying malicious URLs in webhook messages, an attacker forces the vulnerable server to initiate HTTP requests on behalf of itself toward internal network resources that are typically inaccessible from the public internet. This capability allows for reconnaissance of internal infrastructure, exfiltration of sensitive data residing behind firewalls or private subnets, and potentially chaining this vulnerability with other flaws to achieve remote code execution if specific parsing libraries are vulnerable to deserialization or command injection via URL parameters. The ability to inject arbitrary messages also disrupts the integrity of automated workflows managed by the agent pipeline, leading to potential denial of service or manipulation of business logic dependent on accurate webhook data.
From a classification perspective, this vulnerability aligns with CWE-287 Improper Authentication and CWE-345 Insufficient Verification of Data Authenticity as defined in the Common Weakness Enumeration standard. The failure to validate signatures constitutes a direct violation of integrity requirements for external interfaces. Furthermore, the exploitation technique involving server-side request forgery maps directly to MITRE ATT&CK Technique T1105 Ingress Tool Transfer and potentially T1498 Network Denial of Service if the forged requests are used to flood internal services. The lack of access control on webhook handlers is a common misconfiguration in API-driven applications, often stemming from developers assuming that webhooks are only accessed by trusted partners without implementing robust verification steps.
Mitigation strategies must prioritize immediate remediation of the authentication gap and implementation of strict input validation. Developers should enforce signature-based authentication for all webhook endpoints using industry-standard algorithms such as HMAC-SHA256 to verify message integrity and origin. Additionally, access control lists or API gateways should be configured to restrict endpoint accessibility to known IP ranges if possible, though this is less effective than cryptographic verification in dynamic environments. It is critical to sanitize and validate all URLs provided in webhook payloads before they are processed by the media fetching module to prevent SSRF attacks. This includes validating URL schemes, blocking requests to private IP address ranges, and ensuring that only whitelisted domains can be accessed. Regular security audits and static code analysis focused on external interface handling will help identify similar weaknesses in other parts of the application architecture before they are exploited in production environments.