# CVE-2026-42084: OpenC3 COSMOS: Hijacked session token can be used to reset password for persistence

> Attackers with a valid session token can reset passwords without the old password, gaining persistent access to hijacked accounts including admin.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 May 2026
- **Updated:** 6 May 2026
- **Also known as:** GHSA-wgx6-g857-jjf7, PYSEC-2026-2242

## What is CVE-2026-42084?

CVE-2026-42084 is a high-severity authentication bypass vulnerability in OpenC3 cosmos, published on 4 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-620 (Unverified Password Change)

## Which versions are affected by CVE-2026-42084?

5 open source packages ship an affected version, including openc3. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `openc3` | PyPI | All versions | 6.10.5 |
| `openc3` | RubyGems | All versions | 6.10.5 |
| `openc3` | RubyGems | All versions | 6.10.5 |
| `openc3` | RubyGems | From 7.0.0.pre.rc1 | 7.0.0-rc3 |
| `openc3` | RubyGems | From 7.0.0.pre.rc1 | 7.0.0-rc3 |

Products: Openc3 Cosmos.

## How do I fix CVE-2026-42084?

Upgrade openc3 to a fixed version for your release line: 6.10.5 or 7.0.0-rc3.

## Is CVE-2026-42084 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42084 exists.

## Other vulnerabilities in OpenC3 cosmos

- [CVE-2025-28386](https://insights.sbomify.com/CVE-2025-28386/): Code injection in n/a (critical 9.8)
- [CVE-2025-28388](https://insights.sbomify.com/CVE-2025-28388/): Hardcoded credentials in n/a (critical 9.8)
- [CVE-2025-28389](https://insights.sbomify.com/CVE-2025-28389/): Weak cryptography in n/a (critical 9.8)
- [CVE-2026-42087](https://insights.sbomify.com/CVE-2026-42087/): OpenC3 COSMOS: SQL Injection in QuestDB Time-Series Data Base (critical 9.6)
- [CVE-2026-42088](https://insights.sbomify.com/CVE-2026-42088/): OpenC3 COSMOS: Administrative Actions via the Script Runner Tool (critical 9.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42084 and fix it if it is affected.

What it is: CVE-2026-42084 is a high-severity authentication bypass vulnerability in OpenC3 cosmos, published on 4 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42084 exists.

Affected packages and fixed versions:
- openc3 (PyPI): affected all versions; fixed in 6.10.5
- openc3 (RubyGems): affected all versions; fixed in 6.10.5
- openc3 (RubyGems): affected all versions; fixed in 6.10.5
- openc3 (RubyGems): affected from 7.0.0.pre.rc1; fixed in 7.0.0-rc3
- openc3 (RubyGems): affected from 7.0.0.pre.rc1; fixed in 7.0.0-rc3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-42084/ (Markdown: https://insights.sbomify.com/CVE-2026-42084/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42084
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42084
- OSV: https://osv.dev/vulnerability/CVE-2026-42084

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42084/
Summaries are generated and may contain mistakes; the official description above is the record.