Lemur Security Bulletin: Fixes for SSRF, JWT Algorithm Confusion, Plaintext Password Storage, and Privilege Escalation

Vulnerability Overview 1. SSRF Vulnerability: - Description: In , user-supplied directory URLs were fetched server-side without validation, allowing access to IMDS and internal networks. - Fix: is now validated against at the time of authorization creation. The default allowlist covers pre-configured Let's Encrypt and GTS; operators can extend this to configure internal or additional ACME CAs. 2. JWT Algorithm Confusion Vulnerability: - Description: In , the JWT validator accepted algorithm names from unsigned token headers rather than fixing them server-side. The server now reads the algorithm list from (defaulting to ), which is the only algorithm historically used by Lemur. Deployments do not need to ensure full backward compatibility by default, and no configuration changes are required. 3. Post-Authentication SSRF Vulnerability: - Description: In , CRL Distribution Point URLs and OCSP Responder URLs extracted from uploaded certificate extensions were used as network destinations without validation. and now reject RFC1918, loopback, and link-local destinations before making outbound requests. Operators can optionally configure the and allowlists. The module-level is now limited to 1,000 entries to prevent unbounded cache growth. 4. Plaintext Password Storage Vulnerability: - Description: In , wrote new passwords to the database without hashing. The SQLAlchemy event listener was missing, bypassing the bcrypt hashing applied during insertion every time an administrator triggered a password reset. Passwords are now stored after hashing. Any password resets performed previously should be considered leaked and rotated. After upgrading, run to detect and re-hash plaintext passwords already present in the database. 5. Privilege Escalation Vulnerability: - Description: In , any member of a role could override the role's member list, rename the role, or add arbitrary users via . The endpoint now requires administrative permissions, consistent with the existing handler. 6. Role Enforcement Bypass: - Description: Fixed from version 1.9.1. The original fix set to , which broke normal user operations (such as certificate issuance and notification management) for any deployment where users were assigned custom group roles instead of the built-in or roles. By design, Lemur allows any authenticated user to perform write operations; roles are an explicit opt-in restriction for users who should only have read access. The correct fix now ensures that explicitly denies any authenticated user holding a role, while allowing other authenticated users. has been restored to its default value of . Setting it to restricts write access to and roles, as previously described. remains (authority creation is an administrative operation). Note that by design, any authenticated user (those not assigned a role) retains write access to notifications, certificate uploads, and domain management. Operators in higher-assurance environments should evaluate setting to restrict these operations to and users. See the documentation for details. Impact Scope SSRF Vulnerability: Affects all users utilizing , particularly those using internal networks or IMDS. JWT Algorithm Confusion Vulnerability: Affects all users utilizing JWT verification, particularly those relying on the default algorithm list. Post-Authentication SSRF Vulnerability: Affects all users utilizing CRL Distribution Point and OCSP Responder URLs, particularly those targeting RFC1918, loopback, and link-local destinations. Plaintext Password Storage Vulnerability: Affects all users utilizing the password reset functionality, particularly those using administrator-driven password resets. Privilege Escalation Vulnerability: Affects all users utilizing role management, particularly those allowing role members to overwrite role lists. Role Enforcement Bypass: Affects all users utilizing role enforcement, particularly those using custom group roles. Remediation 1. SSRF Vulnerability: - Validate at authorization creation time against . - Operators can extend the allowlist to configure internal or additional ACME CAs. 2. JWT Algorithm Confusion Vulnerability: - Read the algorithm list from (defaults to ). - Deployments do not need to ensure full backward compatibility by default, and no configuration changes are required. 3. Post-Authentication SSRF Vulnerability: - and now reject RFC1918, loopback, and link-local destinations. - Operators can optionally configure the and allowlists. - The module-level is now limited to 1,000 entries. 4. Plaintext Password Storage Vulnerability: - Passwords are now stored after hashing. - Any previously reset passwords should be considered leaked and rotated. - After upgrading, run to detect and re-hash plaintext passwords already present in the database. 5. Privilege Escalation Vulnerability: - The endpoint now requires administrative permissions. 6. Role Enforcement Bypass: - has been restored to the default . - Setting it to restricts write access to and

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Lemur Security Bulletin: Fixes for SSRF, JWT Algorithm Confusion, Plaintext Password Storage, and Privilege Escalation

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