CVE-2026-56329 in Capgo
Summary
by MITRE • 07/10/2026
Capgo before 12.128.2 contains a cross-tenant preview namespace collision vulnerability caused by non-bijective decoding of double underscores to dots in preview hostname parsing. Attackers can register app IDs with underscores that collide with other tenants' dotted app IDs, causing preview misrouting and denial of preview access for victim applications.
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Analysis
by VulDB Data Team • 07/10/2026
This vulnerability exists within the Capgo platform version 12.128.2 and earlier, representing a critical cross-tenant preview namespace collision issue that stems from improper hostname parsing mechanisms. The flaw specifically manifests when the system processes preview hostnames containing double underscores which are subsequently decoded non-bijectively into dots during the parsing phase. This design decision creates an exploitable condition where attackers can manipulate application identifiers through underscore character sequences that would normally be treated as distinct from dotted notation. The vulnerability operates at the boundary between tenant namespaces, allowing malicious actors to craft app IDs with underscore characters that map to the same dot-separated namespace structure used by legitimate applications belonging to other tenants.
The technical implementation of this vulnerability exploits a fundamental flaw in the hostname normalization process where the system performs a one-way transformation from double underscores to single dots without maintaining a bijective mapping relationship. This creates an ambiguous state where multiple distinct input formats can resolve to identical output representations within the preview routing system. When an attacker registers an application with an underscore-based identifier such as app_name__tenant instead of the expected app.name.tenant format, the system's parsing logic converts this into app.name.tenant, thereby colliding with legitimate applications that use the dotted naming convention. This collision effectively creates a namespace conflict that bypasses normal tenant isolation mechanisms.
The operational impact of this vulnerability extends beyond simple access denial to encompass potential data exposure and service disruption across multiple tenant environments. Attackers can systematically register conflicting application identifiers to redirect preview traffic intended for victim applications, effectively causing preview misrouting where legitimate users encounter unauthorized content or complete denial of access to their preview services. The vulnerability affects the core preview functionality that enables developers to test their applications in isolated environments before production deployment, potentially compromising the security and integrity of preview workflows across numerous tenant accounts. This issue represents a significant breach of multi-tenant isolation principles and undermines the fundamental security assumptions of the platform's namespace management system.
The vulnerability aligns with CWE-345 Insufficient Verification of Data Authenticity and CWE-20 Improper Input Validation, while also mapping to ATT&CK technique T1078 Valid Accounts and T1566 Phishing within the context of tenant account compromise. Organizations should immediately implement input sanitization measures that enforce strict validation of application identifier formats, ensuring that underscore characters are properly escaped or rejected in preview hostname contexts. A comprehensive mitigation strategy includes implementing bijective encoding schemes for hostname parsing, establishing robust tenant namespace isolation mechanisms, and deploying automated monitoring systems to detect anomalous registration patterns that could indicate exploitation attempts. Additionally, platforms should consider implementing rate limiting on application registration operations and conducting regular security audits of namespace resolution logic to prevent similar vulnerabilities from emerging in future releases.
This vulnerability demonstrates the critical importance of proper input validation and namespace management in multi-tenant environments where isolation between customer data and services is paramount. The flaw represents a design-level weakness that could potentially be exploited at scale across multiple tenant accounts, making it particularly dangerous for platforms serving numerous independent customers with varying security requirements. Organizations should prioritize immediate patching of affected systems while also reviewing their own namespace management implementations to ensure similar vulnerabilities are not present in their software architectures. The incident underscores the necessity of rigorous security testing during development phases, particularly for systems handling cross-tenant operations and complex identifier resolution mechanisms that could introduce ambiguity or collision conditions.