OneUptime is an open-source monitoring and observability platform. Prior to version 10.0.42, OneUptime's SAML SSO implementation (App/FeatureSet/Identity/Utils/SSO.ts) has decoupled signature verification and identity extraction. isSignatureValid() verifies the first <Signature> element in the XML DOM using xml-crypto, while getEmail() always reads from assertion[0] via xml2js. An attacker can prepend an unsigned assertion containing an arbitrary identity before a legitimately signed assertion, resulting in authentication bypass. This issue has been patched in version 10.0.42.
Use CWE-347, Hackerbay vendor hub and Oneuptime product page to widen CVE-2026-34840 into its surrounding weakness, vendor, and product context.
Compare it with CVE-2026-33396, CVE-2026-32306 and CVE-2026-35053 for nearby disclosures in the same product family.