Critical severity · published Aug 28, 2026
CVE-2026-18918
OAuth 1.0 session-fixation chain via unauthenticated provisional-consumer registration and insecure v1_0Allowed default
9.1
CVSS
0.5%
EPSS
No
On KEV
Description
In Eclipse Lyo versions 2.0.0 to 7.0.0, OAuth server authorization checks can be bypassed when the 2-legged auth is supported by the server. In those cases, application that based their authz filters upon Lyo-provided `AbstractAdapterCredentialsFilter`, are vulnerable. An attacked can create a provisional trusted client (valid use-case) but then it can be used as a trusted client immediately without requiring the administrator approval to clear the provisional status. The 3-legged path requiring user interaction is not vulnerable and rejects provisional clients.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 43% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
EL
Eclipse Lyo · Eclipse Foundation
2.0.0 before 7.0.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-18918
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-18918
github.com
https://github.com/eclipse-lyo/lyo/releases/tag/v6.0.1.Final
github.com
https://github.com/eclipse-lyo/lyo/releases/tag/v7.0.0.Beta3
gitlab.eclipse.org
https://gitlab.eclipse.org/security/cve-assignment/-/work_items/221
