Shepherd through 0.3.1 SSRF via DNS Rebinding in Citation Checker

Advisories

Shepherd through 0.3.1 SSRF via DNS Rebinding in Citation Checker

severity: low
date: 10/11/2026
Affecting: Shepherd <= 0.3.1
CVE: CVE-2026-108741
CWE: CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
CVSS: 2.3
CVSS V4 Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
References: https://hackmd.io/@haind03/shepherd-citation-checker-dns-rebinding-ssrf
https://github.com/shepherd-agents/shepherd/blob/d34d5ca334871dfcb5a3dc76dd78045829fa4e56/shepherd/extras/citation-checker/src/shepherd_citation_checker/_engine/network.py#L9-L17
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
Credit: HaiND from the Post and Telecommunication Institute of Technology
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.

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