Vulnerability · Published Apr 2, 2026 · Assigned by GitHub_M

CVE-2026-34840OneUptime SSO: Multi-Assertion Identity Injection via Decoupled Signature Verification

High 8.1

In plain English

A high-severity security flaw in oneuptime from OneUptime. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities).

Severity (CVSS 3.1)8.1High

Exploit odds (30 days)0.3%top 80.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

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.

Affected products (as reported)

Vendor	Product	Versions
OneUptime	oneuptime	< 10.0.42

Weakness: CWE-347 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

References

https://github.com/OneUptime/oneuptime/security/advisories/GHSA-5w5c-766x-265g x_refsource_CONFIRM
https://github.com/OneUptime/oneuptime/commit/2fd7ede52f60444710628d6c1b34dee2ef9e57d1 x_refsource_MISC
https://github.com/OneUptime/oneuptime/releases/tag/10.0.42 x_refsource_MISC