CVE-2026-109345
Description
A flaw was found in DOMPurify. This vulnerability allows a remote attacker to conduct cross-site scripting (XSS) attacks by bypassing HTML sanitization when the library operates in in-place mode. When processing raw text elements containing embedded markup, the library removes the element but fails to neutralize its text content before returning the node. If the application subsequently serializes and re-parses the returned content, the embedded script executes within the user's browser session.
Statement
A flaw of moderate impact was found in the DOMPurify HTML sanitization library, which is used by components in the Red Hat Hardened Images (Hummingbird) product. When DOMPurify operates in in-place mode, it force-removes a raw text element such as a style element but returns the node without neutralizing its text content. A remote attacker with no privileges can supply a crafted raw text element whose text content still carries markup, such as a closing style tag followed by an img onerror payload. If the application subsequently serializes and re-parses the returned node and a victim renders the result, the embedded script executes in the victim's browser session, allowing access to browser-session data and unauthorized actions on the victim's behalf. Red Hat Product Security rated this flaw Moderate with a CVSS 6.1 score, consistent with the upstream severity. Within Red Hat, this flaw was tracked only against Red Hat Hardened Images (Hummingbird) components that bundle the npm dompurify package; assessment was delegated to the responsible business unit, which determined those components are not affected because the vulnerable code is not present.
Mitigation
This flaw only manifests when DOMPurify is used with the IN_PLACE option and the application subsequently serializes and re-parses the returned node. Applications can avoid the vulnerable path by not enabling the IN_PLACE option (using DOMPurify's default sanitization, which returns a newly sanitized node) and by not serializing and re-parsing the content of the returned node. As a permanent resolution, upgrade to dompurify 3.4.16 or later, which contains the fix for this issue.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.1 | N/A | 6.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Changed | N/A | Changed |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Understanding the Weakness (CWE)
Access Control,Confidentiality
Technical Impact: Bypass Protection Mechanism; Read Application Data
The most common attack performed with cross-site scripting involves the disclosure of private information stored in user cookies, such as session information. Typically, a malicious user will craft a client-side script, which -- when parsed by a web browser -- performs some activity on behalf of the victim to an attacker-controlled system (such as sending all site cookies to a given E-mail address). This could be especially dangerous to the site if the victim has administrator privileges to manage that site. This script will be loaded and run by each user visiting the web site. Since the site requesting to run the script has access to the cookies in question, the malicious script does also.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
In some circumstances it may be possible to run arbitrary code on a victim's computer when cross-site scripting is combined with other flaws, for example, "drive-by hacking."
Confidentiality,Integrity,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Read Application Data
The consequence of an XSS attack is the same regardless of whether it is stored or reflected. The difference is in how the payload arrives at the server. XSS can cause a variety of problems for the end user that range in severity from an annoyance to complete account compromise. Some cross-site scripting vulnerabilities can be exploited to manipulate or steal cookies, create requests that can be mistaken for those of a valid user, compromise confidential information, or execute malicious code on the end user systems for a variety of nefarious purposes. Other damaging attacks include the disclosure of end user files, installation of Trojan horse programs, redirecting the user to some other page or site, running "Active X" controls (under Microsoft Internet Explorer) from sites that a user perceives as trustworthy, and modifying presentation of content.
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