JetBrains TeamCity EUVD-2026-33384

Exploitation requires the SAML SSO plugin to be enabled and actively configured in the TeamCity instance - this is not the default authentication mode and must be explicitly set up by administrators. The attacker must be able to submit a crafted SAML response to the TeamCity SAML authentication endpoint, which typically requires either a man-in-the-middle position between the Identity Provider and TeamCity, or the ability to operate a malicious IdP that TeamCity has been configured to trust. CVSS PR:N confirms no prior account credentials on TeamCity are required once the SAML endpoint is reachable. Exploitation is strictly limited to TeamCity deployments using SAML-based federation; instances using native TeamCity credentials, LDAP, or other non-SAML authentication are not affected by this vulnerability.

The CVSS 6.5 (Medium) score is underpinned by a vector of AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N - network-accessible, low complexity, requiring no privileges or user interaction, with partial confidentiality and integrity impact. While the CVSS score is medium, the authentication bypass tag significantly elevates real-world risk in practice: unauthorized access to a CI/CD system can enable supply chain compromise far beyond what C:L/I:L implies. No EPSS data was provided, so exploitation probability cannot be quantified. There is no CISA KEV listing and no known POC at time of analysis. A critical limiting factor is that exploitation requires SAML SSO to be actively configured - a non-default deployment mode - which restricts the vulnerable population to organizations using federated identity with TeamCity. CVSS PR:N confirms no prior authentication is required once the attacker can reach the SAML endpoint. Overall: meaningful risk for organizations using SAML SSO; lower practical priority for native-auth deployments.

An attacker with network access to a TeamCity instance configured with SAML SSO crafts a SAML assertion containing a manipulated username attribute - either by acting as a rogue IdP trusted by the target or by intercepting and modifying an IdP response. TeamCity's SAML plugin fails to sufficiently validate the username, accepting the assertion and granting the attacker access as the impersonated user, potentially a project administrator with access to build pipelines, secrets, and source integrations. No public exploit code has been identified at time of analysis.