CVE-2025-25062

MediumPublic PoC

Published: 03 February 2025

Published

03 February 2025

Modified

23 January 2026

KEV Added

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Patch

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CVSS Score 4.4 CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS Score 0.2841 96.6th percentile

Risk Priority 26 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2025-25062 is a medium-severity Cross-site Scripting (CWE-79) vulnerability in Backdropcms Backdrop Cms. Its CVSS base score is 4.4 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 3.4% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-15 (Information Output Filtering).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 2 other techniques. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

Enforces validation of long text content inputs from node or comment forms, directly preventing injection of malicious HTML and JavaScript into CKEditor 5.

SI-15 Information Output Filtering good match

prevent

Filters output of stored content when loaded into the CKEditor 5 editor for administrative editing, blocking execution of injected scripts.

SI-2 Flaw Remediation good match

prevent

Requires timely patching of the CKEditor 5 flaw as recommended in the Backdrop CMS security advisory, eliminating the vulnerability root cause.

MITRE ATT&CK Enterprise TechniquesAI

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 →

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 →

Why these techniques?

Stored XSS in web app enables exploitation of public-facing application (T1190) to inject JS that runs in admin browser, directly facilitating browser session hijacking (T1185) and theft of web session cookies (T1539) as described.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

An XSS issue was discovered in Backdrop CMS 1.28.x before 1.28.5 and 1.29.x before 1.29.3. It doesn't sufficiently isolate long text content when the CKEditor 5 rich text editor is used. This allows a potential attacker to craft specialized HTML…

and JavaScript that may be executed when an administrator attempts to edit a piece of content. This vulnerability is mitigated by the fact that an attacker must have the ability to create long text content (such as through the node or comment forms) and an administrator must edit (not view) the content that contains the malicious content. This problem only exists when using the CKEditor 5 module.

Deeper analysisAI

CVE-2025-25062 is a stored cross-site scripting (XSS) vulnerability, classified under CWE-79, affecting Backdrop CMS versions 1.28.x prior to 1.28.5 and 1.29.x prior to 1.29.3. The issue arises in the CKEditor 5 rich text editor module, where long text content is not sufficiently isolated, allowing attackers to inject specialized HTML and JavaScript. It has a CVSS v3.1 base score of 4.4 (AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N), indicating medium severity with network accessibility but high attack complexity, low privileges required, user interaction needed, and changed scope for limited confidentiality and integrity impacts.

An authenticated attacker with low privileges, such as the ability to create long text content via node or comment forms, can exploit this by embedding malicious payloads. The payload executes only when an administrator edits—rather than merely views—the affected content, potentially leading to theft of admin session data or manipulation of the admin's browser context. Exploitation requires the CKEditor 5 module to be enabled and relies on the admin's interaction.

The official Backdrop CMS security advisory (backdrop-sa-core-2025-001) recommends upgrading to Backdrop CMS 1.28.5 or 1.29.3 to mitigate the vulnerability. Additional details on the issue, including proof-of-concept exploitation, are available in third-party analyses such as those on Medium and GetAstra.