Shlink through 5.1.6 fails to enforce API key role restrictions when issuing Mercure subscription tokens, allowing restricted keys to subscribe to all topics. Attackers with author-only or domain-only keys can access the mercure-info endpoint to receive visit data including referrer, user agent, geolocation, and full short URL objects for URLs outside their authorization boundary.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
None
No data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
Vulnerable Products
shlinkio:shlink
References 5
https://github.com/shlinkio/shlink
disclosure@vulncheck.com
https://github.com/shlinkio/shlink-common/blob/main/src/Mercure/LcobucciJwtProv…
disclosure@vulncheck.com
https://github.com/shlinkio/shlink/blob/v5.1.6/module/Rest/src/Action/MercureIn…
disclosure@vulncheck.com
https://github.com/shlinkio/shlink/issues/2633
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/shlink-through-5.1.6-mercure-token-authori…
disclosure@vulncheck.com