Shepherd (shepherd-ai) through 0.3.1 contains a server-side request forgery guard bypass in the citation-checker extra because the public_url guard validates a resolved address but fetch re-resolves the hostname at connect time. Attackers who plant a crafted reference URL in a checked document and control its DNS can rebind it to internal addresses, sending GET requests to internal HTTP(S) services and capturing responses in evidence files.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
Present
Additional conditions required
Privileges Required
None
No privileges needed
User Interaction
Passive
Minimal interaction
Impact Assessment
Confidentiality
Low
Partial data leak
Integrity
None
No data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
References 5
https://github.com/shepherd-agents/shepherd
disclosure@vulncheck.com
https://github.com/shepherd-agents/shepherd/blob/d34d5ca334871dfcb5a3dc76dd7804…
disclosure@vulncheck.com
https://github.com/shepherd-agents/shepherd/blob/d34d5ca334871dfcb5a3dc76dd7804…
disclosure@vulncheck.com
https://hackmd.io/@haind03/shepherd-citation-checker-dns-rebinding-ssrf
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/shepherd-through-0.3.1-ssrf-via-dns-rebind…
disclosure@vulncheck.com