CVE-2026-25138 — rucio-webui
MEDIUMCVE-2026-25138 is a medium-severity (CVSS 5.3) CWE-204 vulnerability in rucio-webui. A fix is available for rucio-webui — see the affected versions and patch details below.
Rucio WebUI has Username Enumeration via Login Error Message
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-25138.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
rucio-webui🐍rucio-webui🐍rucio-webuiReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The WebUI login endpoint returns distinct error messages depending on whether a supplied username exists, allowing unauthenticated attackers to enumerate valid usernames.
Details
When submitting invalid credentials to /ui/login, the WebUI responds with different error messages based on the existence of the provided username (identity). A non-existent username results in an error indicating that no account is associated with the identity, while an existing username with an incorrect password produces a different authentication-related error.
This behavioral difference allows an attacker to distinguish valid usernames from invalid ones by observing the response content.
Proof of Concept
Bogus Login (Non-existent Username "15251087")
Response contains:
Cannot get find any account associated with 15251087 identity.
Bogus Login (Existing Username "root", Wrong Password)
Response contains:
Cannot get auth token. It is possible that the presented identity root is not mapped to any Rucio account root.
The difference in error messages confirms whether a username exists.
Impact
An unauthenticated attacker can enumerate valid usernames, which may be leveraged for targeted password guessing, credential stuffing, or social engineering attacks.
Remediation / Mitigation
Return a generic authentication failure message for all login errors, regardless of whether the username exists. Avoid disclosing account or identity existence through error responses. Consider implementing rate limiting or additional login throttling to further reduce abuse.
Reources:
- OWASP Authentication Cheat Sheet - Authentication and Error Messages: https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html#authentication-and-error-messages
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | rucio-webui | all versions | 35.8.3pip install --upgrade 'rucio-webui==35.8.3' |
| 🐍PyPI | rucio-webui | ≥ 36.0.0rc1&&< 38.5.4 | 38.5.4pip install --upgrade 'rucio-webui==38.5.4' |
| 🐍PyPI | rucio-webui | ≥ 39.0.0rc1&&< 39.3.1 | 39.3.1pip install --upgrade 'rucio-webui==39.3.1' |
Affected Products
ruciocernDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rucio-webui, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update rucio-webui to 35.8.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25138 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.
Frequently Asked Questions
Is CVE-2026-25138 in your dependencies?
Find it across PyPI, including transitive dependencies.