CVE-2026-34840Public exploitNetwork attack vector

Authenticated impersonation via mismatched SAML assertion handling

Published Apr 2, 2026 · Updated Apr 2, 2026

Authentication bypass in OneUptime before 10.0.42 allows remote authenticated users to impersonate registered SSO users via SAML. The SSO utility verifies the first XML Signature anywhere in the response but getEmail() extracts the NameID from assertion[0], so an unsigned leading assertion is trusted alongside a signed second assertion. Exploitation requires a valid IdP account, assertion-level signatures, and a target identity registered in the same SSO-enabled project; response-level-only signatures block this path.

CVSS severity8.1
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in OneUptime before 10.0.42 allows remote authenticated users to impersonate registered SSO users via SAML. The SSO utility verifies the first XML Signature anywhere in the response but getEmail() extracts the NameID from assertion[0], so an unsigned leading assertion is trusted alongside a signed second assertion. Exploitation requires a valid IdP account, assertion-level signatures, and a target identity registered in the same SSO-enabled project; response-level-only signatures block this path.

The record

CVE
CVE-2026-34840
Published
Apr 2, 2026
Updated
Apr 2, 2026
Vendor
OneUptime
Product
OneUptime
Classifications
CWE-347, T1078
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 10.0.42

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

OneUptime · OneUptimeversion=< 10.0.42

Published CVSS scores

8.1GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
T1078Valid Accounts

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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