Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to… (CVE-2026-66843)
CVE-2026-66843 is a low-severity vulnerability in the html_sanitize_ex library by rrrene. It involves the inclusion of functionality from an untrusted control sphere via the data attribute of an <object> element in sanitized HTML. This allows a remote attacker to load arbitrary documents into a trusted page. However, this is not unconditional cross-site scripting, as javascript: URLs do not execute through <object data> in current browsers, and data: documents load in an opaque origin. Exploitation requires the application to serve attacker-controlled content from a same-origin path.
AI Analysis
Technical Summary
The vulnerability in html_sanitize_ex arises because the <object> element, which can carry a URI via its data attribute, is not properly registered or filtered through allow_tag_with_uri_attributes/3. The only guard is a prefix match on lowercase "javascript:", which fails to block mixed-case variants, data: URIs, protocol-relative URLs, and same-origin paths. This allows an attacker to load arbitrary documents into a trusted page via the data attribute of <object>. The issue affects versions from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.
Potential Impact
An attacker can cause a trusted page to load a document of their choosing via the <object data> attribute in sanitized HTML. This does not lead to unconditional cross-site scripting because javascript: URLs do not execute in this context, and data: URIs load in an opaque origin. Full script execution requires the application to serve attacker-controlled content from a same-origin path. The overall impact is limited, reflected by a low CVSS score of 2.3.
Mitigation Recommendations
No official patch links are provided in the data. The vulnerability affects versions >=0.3.1 <1.5.3 and 1.5.0-rc.0, so upgrading to version 1.5.3 or later is implied to remediate the issue. Since this is a library, users should update to a fixed version once available. Patch status is not explicitly confirmed in the provided data; therefore, check the vendor advisory for current remediation guidance.
Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to… (CVE-2026-66843)
Description
CVE-2026-66843 is a low-severity vulnerability in the html_sanitize_ex library by rrrene. It involves the inclusion of functionality from an untrusted control sphere via the data attribute of an <object> element in sanitized HTML. This allows a remote attacker to load arbitrary documents into a trusted page. However, this is not unconditional cross-site scripting, as javascript: URLs do not execute through <object data> in current browsers, and data: documents load in an opaque origin. Exploitation requires the application to serve attacker-controlled content from a same-origin path.
CVSS v3.1
Score 6.1medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in html_sanitize_ex arises because the <object> element, which can carry a URI via its data attribute, is not properly registered or filtered through allow_tag_with_uri_attributes/3. The only guard is a prefix match on lowercase "javascript:", which fails to block mixed-case variants, data: URIs, protocol-relative URLs, and same-origin paths. This allows an attacker to load arbitrary documents into a trusted page via the data attribute of <object>. The issue affects versions from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.
Potential Impact
An attacker can cause a trusted page to load a document of their choosing via the <object data> attribute in sanitized HTML. This does not lead to unconditional cross-site scripting because javascript: URLs do not execute in this context, and data: URIs load in an opaque origin. Full script execution requires the application to serve attacker-controlled content from a same-origin path. The overall impact is limited, reflected by a low CVSS score of 2.3.
Mitigation Recommendations
No official patch links are provided in the data. The vulnerability affects versions >=0.3.1 <1.5.3 and 1.5.0-rc.0, so upgrading to version 1.5.3 or later is implied to remediate the issue. Since this is a library, users should update to a fixed version once available. Patch status is not explicitly confirmed in the provided data; therefore, check the vendor advisory for current remediation guidance.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-6g7x-33rf-28v3
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-66843"]
- Database Specific Severity
- LOW
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a7b6fd2bf8831d5393ea910
Added to database: 08/11/2026, 18:54:10 UTC
Last enriched: 08/19/2026, 15:05:53 UTC
Last updated: 09/26/2026, 01:47:43 UTC
Views: 74
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