Chartbrew allows users to create charts from data sources and share them via tokens. A vulnerability in versions prior to 5.2.3 permits an attacker who knows the application's CB_SECRET to forge chart‑share tokens and bypass the share-token verification, enabling access to private charts that have been shared at least once. This leads to discovery of sensitive chart data such as chartData through unauthenticated requests, representing a disclosure of confidential information (CWE‑347).

The flaw affects all installations of Chartbrew that have not upgraded to v5.2.3 and that use the default or a known CB_SECRET value, including stock Docker‑Compose images and source distributions. Private charts that have been shared create a share‑policy row that the attacker can target, and the filter‑access route accepts sequential numeric chart IDs without validating a legitimate share link. Any deployment where the secret is unchanged and shared charts exist is vulnerable.

The CVSS score of 7.5 indicates a high severity. Although the EPSS score is not available, the vulnerability can be exploited without authentication once the secret is known, and existing share‑policy rows enable enumeration of chart IDs. The flaw is not listed in CISA's KEV catalog, but the potential for data loss in applications that expose sensitive metrics makes it a critical concern for users who rely on Chartbrew for confidential visualizations.