High severity · published Apr 2, 2026
CVE-2026-34840
OneUptime SSO: Multi-Assertion Identity Injection via Decoupled Signature Verification
8.1
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 18% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ON
oneuptime · OneUptime
< 10.0.42 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-34840
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-34840
Patch
https://github.com/OneUptime/oneuptime/commit/2fd7ede52f60444710628d6c1b34dee2ef9e57d1
Product
https://github.com/OneUptime/oneuptime/releases/tag/10.0.42
Exploit
https://github.com/OneUptime/oneuptime/security/advisories/GHSA-5w5c-766x-265g
More from oneuptime
9.9
CVE-2026-45102
OneUptime: RCE due to Node.js' vm module escape via error objects and infinite recursion
9.9
CVE-2026-33396
OneUptime has sandbox escape in Synthetic Monitor Playwright runtime allows project members to execute arbitrary commands on Probe
9.9
CVE-2026-32306
OneUptime ClickHouse SQL Injection via Aggregate Query Parameters
9.9
CVE-2026-30957
OneUptime Synthetic Monitor RCE via exposed Playwright browser object
9.9
CVE-2026-30956
OneUptime has authorization bypass via client‑controlled is-multi-tenant-query header