The ZSIRep client library registers a global .NET callback that accepts any certificate for HTTPS connections, bypassing validation (CWE‑295). This flaw permits an attacker who can impersonate the ZSIRep server to intercept or tamper with authentication data and transmitted documents. Because the callback persists after the client disconnects, the vulnerability also weakens other HTTPS connections in the same application process, exposing additional data to potential MITM attacks.

The vulnerability exists in the KAMSOFT ZSIRep Client Library. It is deployed in several KAMSOFT KS products, including KS‑SOMED (fixed in 2026.03.0.01), KS‑PPS (fixed in 2026.03.1.0), KS‑MEDIS (fixed in 2026.03.0.0), KS‑SOLAB (fixed in 2026.3.1.0), and KS‑ASW (fixed in 2026.3.0.1).

The CVSS score of 5.3 indicates moderate severity. EPSS is not available and the vulnerability is not listed in the CISA KEV catalog, suggesting no reported exploitation yet. The likely attack vector is any network path to a ZSIRep server; an attacker who controls or presents a forged server can cause the library to accept a bogus certificate and execute a MITM, potentially compromising the confidentiality and integrity of transmitted data. Because certificate validation is bypassed automatically, the exploit does not require user interaction once the application runs.