Cyber Resilience

CVE-2026-25136

XSS in Cern Rucio ≤ 35.8.3

Public PoCXSS
Published
25 February 2026
Modified
27 February 2026
Patch / advisory
View advisory
CVSS Score v3.1 8.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
EPSS Score 0.0026 18th percentile
Risk Priority 58 floored blend · peak EPSS

Summary

CVE-2026-25136 is a high-severity Cross-site Scripting (CWE-79) vulnerability in Cern Rucio. Its CVSS base score is 8.1 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Browser Session Hijacking (T1185); ranked at the 18th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SC-23 (Session Authenticity) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-25136 is a reflected Cross-Site Scripting (XSS) vulnerability, classified under CWE-79 and CWE-1004, in Rucio, a software framework for organizing, managing, and accessing large volumes of scientific data. The issue resides in the WebUI component, specifically the rendering of the ExceptionMessage on 500 error pages, affecting all versions prior to 35.8.3, 38.5.4, and 39.3.1.

Attackers without privileges (PR:N) can exploit this vulnerability over the network (AV:N) with low complexity (AC:L) by crafting a malicious URL that triggers a 500 error containing an XSS payload in the ExceptionMessage. Exploitation requires user interaction (UI:R), such as a victim navigating to the URL, after which the payload executes in the victim's browser context. This enables theft of login session tokens, resulting in high impacts to confidentiality and integrity but none to availability (CVSS v3.1 score: 8.1; C:H/I:H/A:N/S:U).

Mitigation is provided via patches in Rucio versions 35.8.3, 38.5.4, and 39.3.1, with release notes available on GitHub. Further details, including the fix implementation, are documented in the project's security advisory at GHSA-h79m-5jjm-jm4q. General XSS prevention strategies are outlined in the OWASP Cross-Site Scripting Prevention Cheat Sheet.

OWASP Top 10 for Web (2025)

A02:2025 Security MisconfigurationA05:2025 Injection

EU & UK References

Vulnerability Data

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…

more

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.

CWE(s)
CWE-79CWE-1004

Related Threats

MITRE ATT&CK Enterprise Techniques

T1185 Browser Session Hijacking Collection
Adversaries may take advantage of security vulnerabilities and inherent functionality in browser software to change content, modify user-behaviors, and intercept information as part of various browser session hijacking techniques.
attack.mitre.org →
T1539 Steal Web Session Cookie Credential Access
An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials.
attack.mitre.org →
T1659 Content Injection Initial Access
Adversaries may gain access and continuously communicate with victims by injecting malicious content into systems through online network traffic.
attack.mitre.org →
T1189 Drive-by Compromise Initial Access
Adversaries may gain access to a system through a user visiting a website over the normal course of browsing.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2023-37901Same vendor: Cern
CVE-2023-25837Shared CWE-79
CVE-2023-22438Shared CWE-79
CVE-2023-27614Shared CWE-79
CVE-2023-47164Shared CWE-79
CVE-2023-49145Shared CWE-79
CVE-2023-47853Shared CWE-79
CVE-2023-28474Shared CWE-79
CVE-2023-37636Shared CWE-79
CVE-2023-1006Shared CWE-79

Affected Assets

cern
rucio
≤ 35.8.3 · 36.0.0 — 38.5.4 · 39.0.0 — 39.3.1

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.1.2
  • V1.3.2

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover missing or incorrect input neutralization through targeted web-application tests.

SC-23 Session Authenticity good match

Proper implementation of session authenticity requires marking sensitive session cookies HttpOnly so that client scripts cannot access them.

SI-10 Information Input Validation good match

Input validation directly enforces neutralization of untrusted data before it reaches web output generation.

SI-15 Information Output Filtering good match

Output filtering can catch or sanitize unneutralized script content before it is served to users.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly target introduction of XSS via coding standards/testing (mostly), yet the single broad outcome leaves many specific neutralization vectors unaddressed (partial).

PR.AT-02 partial match
prevents

Role-based training can reduce the chance developers introduce missing HttpOnly flags but supplies no enforcement or detection, leaving essentially all of the implementation flaw's risk intact.

PR.PS-02 partial match
prevents

Patching and EOL replacement can remediate known XSS instances in libraries or frameworks (partial) but do nothing to enforce input neutralization in application code (none).

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Secure-coding testing and automated code-analysis tools are applied to detect improper neutralization of script-related content during web-page generation.

A.5.6 Contact with special interest groups partial match
prevents

Knowledge exchange on emerging attack techniques and patches reduces the likelihood that cross-site scripting flaws remain unaddressed in deployed applications.

A.5.7 Threat intelligence partial match
prevents

Operational indicators of compromise for web-application attacks can be incorporated into WAF or input-filtering rules, lowering the likelihood that unsanitized data reaches the browser.

A.8.25 Secure development life cycle partial match
prevents

Requiring language-specific secure-coding standards and automated scanning during the SDLC catches missing output encoding or improper neutralization of untrusted data before the software reaches production.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate HttpOnly on sensitive cookies.

A.8.28 Secure coding partial match
prevents

Secure-coding standards, SAST scans and removal of insecure code samples together eliminate the failure to neutralize script content that produces cross-site scripting flaws.

References