A Server-Side Request Forgery (SSRF) bypass vulnerability exists in “stunnel” 5.79 and lower when configured in SOCKS proxy mode. This flaw allows a client to bypass intended localhost restrictions by using IPv4-mapped IPv6 addresses (e.g., “::ffff:127.0.0.1”) or unspecified addresses ("0.0.0.0", "::"), enabling access to loopback-only services on the "stunnel" host that should not be network-reachable.
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Tue, 04 Aug 2026 12:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | A Server-Side Request Forgery (SSRF) bypass vulnerability exists in “stunnel” 5.79 and lower when configured in SOCKS proxy mode. This flaw allows a client to bypass intended localhost restrictions by using IPv4-mapped IPv6 addresses (e.g., “::ffff:127.0.0.1”) or unspecified addresses ("0.0.0.0", "::"), enabling access to loopback-only services on the "stunnel" host that should not be network-reachable. | |
| Title | stunnel: SSRF bypass in stunnel SOCKS proxy via IPv4-mapped IPv6 loopback and unspecified addresses allows access to loopback-only services | |
| Weaknesses | CWE-918 | |
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| Metrics |
threat_severity
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cvssV3_1
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