CVE-2026-70367: Stunnel: ssrf bypass in stunnel socks proxy via ipv4-mapped ipv6 loopback and unspecified addresses allows access to loopback-only services

CSIRTS triage

What: SOCKS proxy in Stunnel can be bypassed via IPv4-mapped IPv6 loopback and unspecified addresses, allowing unauthorized access to loopback-only services.
Who is affected: Stunnel deployments using SOCKS proxy that restrict access to loopback services.
Urgency: Medium priority; SSRF bypass allows circumvention of network access controls on loopback services, though not currently exploited.
Action: Update Stunnel to a patched version that properly validates IPv4-mapped IPv6 addresses in SOCKS proxy filtering.

AI-assisted analysis generated from the source advisory — verify against the original.

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EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-703670.15% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 5% of all EPSS-scored CVEs.

CVE	CSIRTS overview	External
CVE-2026-70367	coverage & exploitation status	NVD · CVE.org

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