GHSA-cj75-f6xr-r4g7
ADVISORY - githubSummary
Summary
There is a possible cross-site scripting vulnerability in rails-html-sanitizer when the sanitizer is configured to allow an SVG reference element such as <use>. See related GHSA-9wjq-cp2p-hrgf in Loofah, whose SVG local-reference logic rails-html-sanitizer mirrors.
- Versions affected:
>= 1.0.3, < 1.7.1 - Not affected:
< 1.0.3 - Fixed versions:
1.7.1
Impact
Rails::HTML::PermitScrubber restricts SVG reference elements in the SVG_ALLOW_LOCAL_HREF collection to local, same-document references, but that restriction covered only the xlink:href attribute. Browsers also accept a plain href attribute per the SVG 2 spec, and it was not restricted, so those elements could reference arbitrary external documents. SVG <use> can load and render external SVG content by reference, and if the referenced document is same-origin and contains scripts, it could execute in the context of the sanitized document. <feImage> can load external images, which can be used for tracking.
Applications are impacted only when the allowed tags are overridden to include one of these SVG reference elements, for example <use> or <feImage>. The default allowed tags do not include these SVG elements, so applications using the default configuration are not affected.
Workarounds
Remove the SVG reference elements (such as use and feImage) from the overridden allowed tags. Applications using the default allowed tags are not affected.
References
- GHSA-9wjq-cp2p-hrgf: SVG
hrefattribute bypasses local-reference restriction in Loofah - CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Credit
Found by maintainer Mike Dalessio during a security audit.
Common Weakness Enumeration (CWE)
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
GitHub
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CVSS SCORE
5.1medium| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| rails-html-sanitizer | gem | - | - | >=1.0.3,<1.7.1 | 1.7.1 |
CVSS:4 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.
The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
Successful exploitation of this vulnerability requires a targeted user to perform specific, conscious interactions with the vulnerable system and the attacker's payload, or the user's interactions would actively subvert protection mechanisms which would lead to exploitation of the vulnerability. Examples include: importing a file into a vulnerable system in a specific manner placing files into a specific directory prior to executing code submitting a specific string into a web application (e.g. reflected or self XSS) dismiss or accept prompts or security warnings prior to taking an action (e.g. opening/editing a file, connecting a device).
There is no loss of confidentiality within the Vulnerable System.
There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Subsequent System.
There is no loss of integrity within the Vulnerable System.
Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Subsequent System.
There is no impact to availability within the Vulnerable System.
There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.