Rucio: Unauthenticated administrator impersonation through SSH challenge tokens

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary SSH challenge tokens are mistakenly accepted as valid credentials during the authentication token validation process. While an SSH challenge token is intended as a short-lived nonce for use in a subsequent SSH key exchange, the function to validate authentication tokens does not differentiate between these and actual authentication tokens. Because challenge tokens are generated based on an account name provided via headers without requiring prior authentication, an unauthenticated attacker can request a valid "challenge" token for any account (including administrative ones) and use it to authenticate against other API endpoints. Proof of Concept The vulnerability exists because SSH challenge tokens are stored in the same database table as regular authentication tokens and validateauthtoken in lib/rucio/core/authentication.py accepts these "challenge" tokens. An attacker can obtain a challenge token for an account such as “root” via the REST API and then present it as a valid…

Published by the source

13 Nov 2026, 01:09 UTC

Last modified by the source

13 Nov 2026, 01:09 UTC

Source last checked

13 Nov 2026, 01:40 UTC

1. Revision 1 · created · 13 Nov 2026

   Published from ghsa record GHSA-x585-4vv8-2mh2

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# Patch Next advisory brief: CVE-2026-100397

Advisory: Rucio: Unauthenticated administrator impersonation through SSH challenge tokens
IDs: CVE-2026-100397, GHSA-x585-4vv8-2mh2
Record: https://patchnext.com/advisories/cve-2026-100397 (revision 1, source checked 13 Nov 2026, 01:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: rucio 41.1.1, 40.4.2, 38.6.1, 35.9.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI rucio: affected >= 1.14.0.post1, < 35.9.1; >= 36.0.0rc1, < 38.6.1; >= 39.0.0rc1, < 40.4.2; >= 41.0.0rc1, < 41.1.1; fixed in 38.6.1, 41.1.1, 40.4.2, 35.9.1

## Suggested inspection (read-only)
- `python -m pip show rucio`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on rucio.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-x585-4vv8-2mh2 (GitHub-reviewed advisory GHSA-x585-4vv8-2mh2 lists affected ranges: PyPI rucio >=1.14.0.post1 =36.0.0rc1 =39.0.0rc1 =41.0.0rc1 <41.1.1)

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