CVE-2026-56318 Overview
CVE-2026-56318 is an information disclosure vulnerability in Capgo versions before 12.128.2. The flaw resides in the /private/validate_password_compliance endpoint, which returns distinct error responses for malformed, non-existent, and existing organization identifiers. Unauthenticated attackers can enumerate valid organization Universally Unique Identifiers (UUIDs) by observing HTTP status codes and error messages. The issue is classified under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor.
Critical Impact
Unauthenticated remote attackers can confirm the existence of organization UUIDs, enabling reconnaissance for targeted attacks against Capgo tenants.
Affected Products
- Capgo versions prior to 12.128.2
- The /private/validate_password_compliance API endpoint
- Multi-tenant Capgo deployments exposing organization UUIDs
Discovery Timeline
- 2026-06-30 - CVE-2026-56318 published to the National Vulnerability Database
- 2026-07-01 - Last updated in the NVD database
Technical Details for CVE-2026-56318
Vulnerability Analysis
The /private/validate_password_compliance endpoint processes organization identifiers supplied in requests. Instead of returning a uniform response for any invalid input, the endpoint differentiates its output based on whether the supplied UUID is malformed, references a non-existent organization, or references an existing organization. Attackers can send crafted requests and observe response status codes along with error message content to distinguish valid organization UUIDs from invalid ones.
The endpoint requires no authentication, so any remote actor with network access can perform enumeration. Confirming organization existence provides reconnaissance value for follow-on attacks such as credential stuffing, targeted phishing, and password policy probing. See the GitHub Security Advisory GHSA-fwwh-rqv7-6pjf and the VulnCheck advisory for additional technical context.
Root Cause
The root cause is inconsistent error handling. The endpoint discloses backend state through response differentiation rather than returning a single opaque response for all invalid inputs. This design allows a side-channel style oracle over the tenant identifier space.
Attack Vector
Exploitation occurs over the network without authentication or user interaction. An attacker iterates candidate UUIDs against the endpoint and classifies responses. Well-formed UUIDs that match existing organizations produce responses distinguishable from those returned for random or malformed UUIDs, allowing systematic enumeration.
No verified exploit code is publicly available. Refer to the vendor advisory for technical details.
Detection Methods for CVE-2026-56318
Indicators of Compromise
- High volumes of requests to /private/validate_password_compliance from a single source address or a small set of addresses.
- Sequential or dictionary-based UUID values in request bodies or query parameters.
- Elevated ratios of 4xx responses correlated with UUID-shaped input patterns.
- Requests to the endpoint from unauthenticated sessions outside expected client applications.
Detection Strategies
- Analyze web server and application logs for repeated access to /private/validate_password_compliance from the same client.
- Alert when the rate of distinct organization UUID values submitted by one source exceeds a defined baseline.
- Correlate response status code distributions per source address to detect oracle-style probing.
Monitoring Recommendations
- Ingest Capgo application and reverse proxy logs into a centralized logging or SIEM platform.
- Build dashboards tracking request volume, unique UUIDs submitted, and response code ratios for the affected endpoint.
- Retain access logs for the endpoint to support post-incident enumeration analysis.
How to Mitigate CVE-2026-56318
Immediate Actions Required
- Upgrade Capgo to version 12.128.2 or later.
- Restrict network access to /private/validate_password_compliance where feasible, limiting it to authenticated sessions or trusted networks.
- Apply rate limiting to the endpoint at the reverse proxy or Web Application Firewall (WAF) layer.
- Review recent access logs for evidence of enumeration activity.
Patch Information
Upgrade to Capgo 12.128.2 or later. The fixed release standardizes error handling on the /private/validate_password_compliance endpoint so that malformed, non-existent, and existing organization identifiers produce indistinguishable responses. See the GitHub Security Advisory GHSA-fwwh-rqv7-6pjf for release details.
Workarounds
- Deploy a WAF rule that rate limits requests to /private/validate_password_compliance per source IP.
- Normalize responses at a reverse proxy by rewriting error status codes and response bodies to a single generic error until the patch can be applied.
- Require authentication on the endpoint via network-level controls where operationally acceptable.
- Monitor and block source addresses that submit large numbers of unique UUID values to the endpoint.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
