CVE-2026-108741: Shepherd through 0.3.1 SSRF via DNS Rebinding in Citation Checker

Severity: low (CVSS 3.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-11 · updated 2026-10-16
Weakness: CWE-367

Description

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.

Affected products

shepherd-agents Shepherd: through 0.3.1

References

https://github.com/shepherd-agents/shepherd
https://github.com/shepherd-agents/shepherd/blob/d34d5ca334871dfcb5a3dc76dd78045829fa4e56/shepherd/extras/citation-checker/src/shepherd_citation_checker/_engine/fetch.py#L34-L55
https://github.com/shepherd-agents/shepherd/blob/d34d5ca334871dfcb5a3dc76dd78045829fa4e56/shepherd/extras/citation-checker/src/shepherd_citation_checker/_engine/network.py#L9-L17
https://hackmd.io/@haind03/shepherd-citation-checker-dns-rebinding-ssrf
https://www.vulncheck.com/advisories/shepherd-through-0.3.1-ssrf-via-dns-rebinding-in-citation-checker

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