CVE-2021-29652 in Pomerium
Summary
by MITRE • 04/02/2021
Pomerium from version 0.10.0-0.13.3 has an Open Redirect in the user sign-in/out process
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Analysis
by VulDB Data Team • 04/08/2021
The vulnerability CVE-2021-29652 affects Pomerium versions 0.10.0 through 0.13.3 and represents a critical open redirect flaw within the user authentication workflow. This issue specifically impacts the sign-in and sign-out processes where the application fails to properly validate redirect URLs, allowing attackers to craft malicious links that could redirect users to arbitrary destinations. The vulnerability stems from insufficient input validation and sanitization of redirect parameters that are used to determine where users should be directed after authentication operations complete.
The technical implementation of this flaw occurs when Pomerium processes authentication callbacks or logout redirects without verifying that the target URLs belong to trusted domains or are properly sanitized. Attackers can exploit this by constructing specially crafted URLs that include malicious redirect parameters, potentially leading to phishing attacks or credential theft. The vulnerability is classified as CWE-601 under open redirect vulnerabilities, which specifically addresses situations where web applications fail to validate redirect destinations, allowing attackers to redirect users to malicious sites. This weakness is particularly dangerous in identity and access management systems where users trust the application interface and may not scrutinize redirect destinations.
The operational impact of this vulnerability extends beyond simple redirection attacks as it can enable sophisticated phishing campaigns where users are tricked into believing they are navigating to legitimate Pomerium interfaces while actually being redirected to attacker-controlled domains. This creates a significant risk for organizations relying on Pomerium for secure access management, as compromised authentication flows can lead to unauthorized access to protected resources. The vulnerability is particularly concerning in enterprise environments where users may have elevated privileges and the redirection could be used to escalate attacks or gain access to sensitive systems. Security frameworks such as MITRE ATT&CK recognize this type of vulnerability under the technique T1566 for phishing and T1071 for application layer protocol usage, highlighting its potential for credential theft and lateral movement.
Organizations should immediately upgrade to Pomerium version 0.13.4 or later where this vulnerability has been addressed through proper input validation and redirect URL sanitization. The fix typically involves implementing strict domain validation for redirect parameters and ensuring that all redirect destinations are either explicitly trusted or properly encoded before being processed. Security teams should also conduct comprehensive audits of all authentication flows to identify similar vulnerabilities and implement proper logging and monitoring of redirect operations to detect potential exploitation attempts. Additionally, user education regarding suspicious redirect behavior and the importance of verifying URLs before authentication should be emphasized as part of a layered defense strategy. The vulnerability demonstrates the critical importance of validating all user-supplied input in authentication flows and highlights the need for security-conscious development practices that prevent common web application vulnerabilities.