Executive brief
SigNoz is an open-source observability platform used to monitor application performance. A security flaw in its Single Sign-On (SSO) system allows attackers to create malicious login links that, when clicked by a legitimate user, send that user's private login session tokens directly to the attacker. This could allow an unauthorized person to take over user accounts and access sensitive monitoring data.
Technical details
An open redirect vulnerability exists in the unauthenticated GET /api/v2/sessions/context endpoint due to insufficient validation of the 'ref' parameter. This parameter is embedded into the OAuth state without cryptographic signing or origin allowlisting. An attacker can craft a login URL containing a 'ref' parameter pointing to a malicious domain; when a victim completes the SSO flow (Google, SAML, or OIDC), the SigNoz server appends the victim's access and refresh tokens to the redirect URL. This allows the attacker to exfiltrate session tokens. A fix has been proposed involving HMAC-SHA256 signing of the OAuth state and strict validation of redirect origins.
Affected products
- SigNoz SigNoz through 0.133.0
Timeline
- 2026-05-23: disclosed: Initial report to vendor security email
- 2026-06-17: disclosed: Public issue opened on GitHub
- 2026-06-24: patched: Pull request with fix submitted
- 2026-07-17: advisory: CVE published to NVD