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

April 22, 2026 (updated May 29, 2026)

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.

References

  • github.com/OpenC3/cosmos/commit/2e623714e3426d5ae81b6f8239d4a2a6937ef776
  • github.com/OpenC3/cosmos/releases/tag/v6.10.5
  • github.com/OpenC3/cosmos/releases/tag/v7.0.0-rc3
  • github.com/OpenC3/cosmos/security/advisories/GHSA-wgx6-g857-jjf7
  • github.com/advisories/GHSA-wgx6-g857-jjf7
  • github.com/rubysec/ruby-advisory-db/blob/master/gems/openc3/CVE-2026-42084.yml
  • nvd.nist.gov/vuln/detail/CVE-2026-42084

Code Behaviors & Features

Detect and mitigate CVE-2026-42084 with GitLab Dependency Scanning

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Affected versions

All versions before 6.10.5, all versions starting from 7.0.0-pre.rc1 before 7.0.0-rc3

Fixed versions

  • 6.10.5
  • 7.0.0-rc3

Solution

Upgrade to versions 6.10.5, 7.0.0-rc3 or above.

Impact 8.1 HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Learn more about CVSS

Weakness

  • CWE-620: Unverified Password Change

Source file

gem/openc3/CVE-2026-42084.yml

Spotted a mistake? Edit the file on GitLab.

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