Sentry versions 21.12.0 through 26.1.0 contain a flaw in the SAML Single Sign-On process that allows an attacker to link a malicious SAML Identity Provider to a different organization on the same Sentry instance. By doing so, the attacker can authenticate as any user within that organization without knowing the user’s credentials. This results in full compromise of the user account, granting the attacker the same permissions as the legitimate user, including data access, modification, and potential administrative actions.

Only self‑hosted Sentry deployments are impacted, and the vulnerability is actionable when either more than one organization is configured or when an attacker has privileges to change SSO settings for another organization in a multi‑organization instance. All affected deployments running any of the versions from 21.12.0 to 26.1.0 are at risk under those conditions.

The CVSS score of 9.1 indicates a critical level of severity, yet the EPSS score of less than 1% suggests a currently low probability of exploitation. The vulnerability is not listed in the CISA KEV catalog. Exploitation is possible remotely; an attacker only needs to craft a forged SAML assertion and initiate the SSO flow against the vulnerable Sentry instance. If successful, the attacker gains full account takeover, potentially leading to uncontrolled access to the organization’s data and resources.