CVE-2026-42084
HIGHCVE-2026-42084 is a high-severity (CVSS 8.1) CWE-620 vulnerability in openc3. O3 Security confirms whether CVE-2026-42084 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
OpenC3 COSMOS: Hijacked session token can be used to reset password for persistence
Blast Radius
openc3💎openc3Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. Prior to versions 6.10.5 and 7.0.0-rc3, the OpenC3 password change functionality allows a user to change their password without providing the old password, by accepting a valid session token instead. In assumed breach scenarios, this behaviour can be exploited by an attacker who has already obtained a valid session token, to gain persistence in hijacked account (including admin) and prevent legitimate users from accessing the account. This issue has been patched in versions 6.10.5 and 7.0.0-rc3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | openc3 | all versions | 6.10.5 |
| 💎RubyGems | openc3 | ≥ 7.0.0.pre.rc1&&< 7.0.0-rc3 | 7.0.0-rc3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openc3. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update openc3 to 6.10.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42084 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-42084 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-42084. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-42084 in your dependencies?
O3 detects CVE-2026-42084 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.