CVE-2026-111235 OpenNMS REST authorization bypass via non-canonical HTTP method
Unauthenticated attackers can bypass REST API authorization to read inventory and modify resources due to case-sensitive HTTP method checks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-111235?
CVE-2026-111235 is a critical authentication bypass vulnerability in The OpenNMS Group Horizon, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
An authorization bypass vulnerability exists in the REST API of multiple versions of OpenNMS Meridian and Horizon. The /rest/** Spring Security filter chains authorize requests with intercept-url rules that name the HTTP method as an uppercase token, compare the method case-sensitively, and have no terminal deny rule. A request that uses a non-canonical (for example lowercase) method token matches no rule and is processed without authentication. A remote, unauthenticated attacker can read the monitored inventory and can create, modify, or delete resources through the REST API, which includes injecting events to fabricate or suppress alarms. The /rest/alarms chain has the same missing deny rule and discloses whether an alarm exists through a difference in the response. The fix adds a terminal deny rule to each REST filter chain.
The solution is to upgrade to Meridian 2024.3.14, 2025.0.11, 2026.0.1 and Horizon 36.0.5 or newer. Meridian and Horizon installation instructions state that they are intended for installation within an organization's private networks and should not be directly accessible from the Internet.
Which versions are affected by CVE-2026-111235?
How do I fix CVE-2026-111235?
No fix has been published for CVE-2026-111235 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-111235 being exploited?
There is no known exploitation of CVE-2026-111235 in the wild and no public exploit code.
Sources
Also known as GHSA-f5w5-g5cw-7w6g.