# CVE-2026-25138: PYSEC-2026-3053 - Rucio WebUI has Username Enumeration via Login Error Message

Source: https://junglewise.ai/threats/cve-2026-25138-rucio-webui-username-enumeration-via-login-error-message  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-13. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-25138 · Severity: low · CVSS 3.1 · Published 2026-07-13

Rucio WebUI is a web-based user interface for the Rucio distributed data management system. The login endpoint returns different error messages depending on whether a supplied username exists, allowing unauthenticated attackers to discover valid usernames. An attacker could use this to build a list of real accounts for targeted password guessing, credential stuffing, or social engineering campaigns.

Technologies: [rucio-webui (PyPI)](https://junglewise.ai/threats/technologies/rucio-webui). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-25138 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-25138 being exploited in the wild.

**How severe is CVE-2026-25138?** Low severity, with a CVSS score of 3.1, published 13 July 2026.

**Which products and versions are affected?** rucio-webui (PyPI) ECOSYSTEM:introduced=0,fixed=35.8.3,introduced=36.0.0rc1,fixed=38.5.4,introduced=39.0.0rc1,fixed=39.3.1; Rucio WebUI before 35.8.3, 38.5.4, 39.3.1.

**Is there a fix for CVE-2026-25138?** Yes. rucio-webui (PyPI): upgrade to 39.3.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-25138 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-25138?** Check whether you run rucio-webui (PyPI) or Rucio WebUI at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- rucio-webui (PyPI): upgrade to 39.3.1 or later

  ```sh
  pip install "rucio-webui>=39.3.1"
  ```


## Technical details

The vulnerability is an information disclosure flaw (CWE-204: Observable Response Discrepancy) in the /ui/login endpoint. When an invalid username is submitted, the system returns a message stating "Cannot get find any account associated with [username] identity," while a valid username with a wrong password returns "Cannot get auth token. It is possible that the presented identity [username] is not mapped to any Rucio account [username]." An unauthenticated attacker can exploit this behavioral difference to enumerate valid usernames by observing response content. The vulnerability requires no privileges, user interaction, or authentication. Patches are available in versions 35.8.3, 38.5.4, and 39.3.1 or later.

## Affected products

- Rucio WebUI before 35.8.3, 38.5.4, 39.3.1

## Identifiers

- CVE-2026-25138
- GHSA-38wq-6q2w-hcf9
- PYSEC-2026-3053

## Timeline

- 2026-02-25: disclosed
- 2026-02-25: patched: Patches released: 35.8.3, 38.5.4, 39.3.1

## References

- [https://github.com/rucio/rucio/security/advisories/GHSA-38wq-6q2w-hcf9](https://github.com/rucio/rucio/security/advisories/GHSA-38wq-6q2w-hcf9)

## Related threats

- [PYSEC-2026-3055 - Rucio WebUI has a Stored Cross-site Scripting (XSS) Vulnerability in its Custom RSE Attribute](https://junglewise.ai/threats/cve-2026-25736-rucio-webui-has-a-stored-cross-site-scripting-xss-vulnerability)
- [PYSEC-2026-3054 - Rucio WebUI has a Stored Cross-site Scripting (XSS) vulnerability its Identity Name](https://junglewise.ai/threats/cve-2026-25735-rucio-webui-has-a-stored-cross-site-scripting-xss-vulnerability)
- [PYSEC-2026-3057 - Rucio WebUI has Stored Cross-site Scripting (XSS) in RSE Metadata](https://junglewise.ai/threats/cve-2026-25734-rucio-webui-has-stored-cross-site-scripting-xss-in-rse-metadata)
- [PYSEC-2026-3058 - Rucio WebUI Vulnerable to Stored Cross-site Scripting (XSS) through Custom Rule Function](https://junglewise.ai/threats/cve-2026-25733-rucio-webui-vulnerable-to-stored-cross-site-scripting-xss-through)
- [PYSEC-2026-3056 - Rucio WebUI has a Reflected Cross-site Scripting Vulnerability](https://junglewise.ai/threats/cve-2026-25136-rucio-webui-has-a-reflected-cross-site-scripting-vulnerability)