CVE-2025-53099 is a medium-severity authentication bypass vulnerability affecting versions of the Sentry error tracking and performance monitoring tool prior to 25.5.0. The vulnerability arises from a race condition and improper handling of OAuth authorization codes within Sentry's authentication flow. Specifically, an attacker who has registered a malicious OAuth application with Sentry can exploit timing issues in the authorization code issuance and redirect process to generate multiple valid authorization codes. These codes can then be exchanged for access and refresh tokens, granting persistent access to a user's account even after the user has de-authorized the malicious application. This flaw is categorized under CWE-288, which involves authentication bypass using alternate paths or channels. The vulnerability requires the attacker to have a low level of privileges (a registered OAuth app) and involves user interaction, but does not require compromising the confidentiality, integrity, or availability of the system directly. The issue has been addressed in Sentry version 25.5.0, and self-hosted users are urged to upgrade. SaaS users of Sentry are not affected due to the patch being applied on the service side. There are no known exploits in the wild at the time of publication, and the CVSS v4.0 score is 5.5, reflecting a medium severity with network attack vector, low attack complexity, partial authentication required, and user interaction needed.

For European organizations using self-hosted Sentry instances, this vulnerability poses a risk of unauthorized persistent access to user accounts via OAuth tokens. Attackers could maintain long-term access to sensitive error tracking and performance data, potentially exposing confidential application diagnostics and user information. This could lead to further lateral movement within the organization’s infrastructure or data leakage. The persistence of access even after de-authorization complicates incident response and remediation efforts. Although the vulnerability does not directly compromise system availability or integrity, the unauthorized access undermines trust in the monitoring infrastructure and could be leveraged for espionage or sabotage. Organizations relying heavily on Sentry for application monitoring and error tracking, especially those in regulated sectors such as finance, healthcare, or critical infrastructure in Europe, may face compliance risks if sensitive data is exposed. The fact that SaaS users are unaffected limits the impact to self-hosted deployments, which are more common in organizations with strict data residency or security policies prevalent in Europe.

European organizations using self-hosted Sentry should immediately upgrade to version 25.5.0 or later to remediate this vulnerability. Beyond patching, organizations should audit all registered OAuth applications for legitimacy and revoke any suspicious or unused apps. Implement strict OAuth app registration policies and monitor OAuth authorization flows for unusual patterns indicative of race condition exploitation. Employ multi-factor authentication (MFA) on user accounts to reduce the risk of token misuse. Network segmentation and access controls should limit the exposure of Sentry instances to only trusted internal networks. Regularly review and rotate OAuth client secrets and tokens to minimize the window of opportunity for attackers. Additionally, implement logging and alerting on OAuth token issuance and de-authorization events to detect anomalies promptly. For organizations with high security requirements, consider deploying runtime application self-protection (RASP) or web application firewalls (WAF) that can detect and block suspicious OAuth flows.