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XSS through oEmbed preview cards

Critical
Gargron published GHSA-ccm4-vgcc-73hp Jul 6, 2023

Package

No package listed

Affected versions

>= 1.3

Patched versions

4.1.3, 4.0.5, 3.5.9

Description

(This advisory describes an issue found by Cure53 as part of an audit performed at Mozilla's request)

Using carefully crafted oEmbed data, an attacker can bypass the HTML sanitization performed by Mastodon and include arbitrary HTML in oEmbed preview cards.

Impact

This introduces a vector for Cross-site-scripting (XSS) payloads that can be rendered in the user's browser when a preview card for a malicious link is clicked through.

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

CVE ID

CVE-2023-36459

Weaknesses

No CWEs

Credits