CVE-2026-121446
Deferred Deferred - Pending Action

SVG Sanitizer CSS Escape Sequence Remote URL Bypass

Publication date: 2026-11-03

Last updated on: 2026-11-03

Assigner: VulnCheck

Description
svg-sanitizer from 0.5.0 before 1.1.0 contains an incomplete filtering vulnerability that allows attackers to bypass remote URL removal by using CSS escape sequences inside url() in SVG presentation attributes. Attackers can supply SVG files with attributes like fill containing escaped slashes that browsers resolve to remote URLs, triggering external requests and enabling data exfiltration.

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Meta Information

Published
2026-11-03
Last Modified
2026-11-03
Generated
2026-11-03
AI Q&A
2026-11-03
EPSS Evaluated
N/A
NVD
CVE-2026-121446
EUVD
EUVD-2026-115868

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
darylldoyle svg-sanitizer 0.5.0

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-791 The product receives data from an upstream component, but does not completely filter special elements before sending it to a downstream component.

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Executive Summary

svg-sanitizer versions 0.5.0 to 1.0.0 have an incomplete filtering vulnerability in SVG presentation attributes. Attackers can bypass URL removal by using CSS escape sequences inside url() functions, such as fill attributes. Browsers resolve these escaped sequences to remote URLs, triggering external requests and enabling data exfiltration.

Detection Guidance

Check SVG files for CSS escape sequences in url() attributes like fill="url(\2f\2f evil.example/x)". Inspect sanitized output for unfiltered remote URLs. Use tools like grep to search for patterns such as url(\\2f\\2f or url(\\/\\/).

Verify library versions of svg-sanitizer. If using Composer, run composer show darylldoyle/svg-sanitizer to check if version is below 1.1.0.

Impact Analysis

This vulnerability allows attackers to trick browsers into making external requests by embedding malicious SVG files. This could lead to data exfiltration, where sensitive information is sent to attacker-controlled servers without user knowledge.

Mitigation Strategies

Upgrade svg-sanitizer to version 1.1.0 or later immediately. If upgrading is not possible, implement additional input validation to block SVG files containing suspicious url() patterns with CSS escapes.

Monitor network traffic for unexpected external requests originating from SVG processing. Disable or restrict SVG rendering in applications if not required.

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