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Vulnerability · Published Aug 4, 2026 · Assigned by redhat

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

Medium 5.4

In plain English

A medium-severity server-side request forgery in stunnel from Mobi-Com Polska Sp. z o.o.. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 13% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.4Medium
Exploit odds (30 days)0.2%top 86.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.24stunnel5.82-r0ALPINE-CVE-2026-70367
Debian:14stunnel3:5.80-1DEBIAN-CVE-2026-70367
Debian:12stunnel4no fix listedDEBIAN-CVE-2026-70367
Debian:13stunnel4no fix listedDEBIAN-CVE-2026-70367

Affected products (as reported)

VendorProductVersions
Mobi-Com Polska Sp. z o.o. stunnel 5.25 – before 5.80
Red Hat Red Hat Enterprise Linux 10 see references
Red Hat Red Hat Enterprise Linux 6 see references
Red Hat Red Hat Enterprise Linux 7 see references
Red Hat Red Hat Enterprise Linux 8 see references
Red Hat Red Hat Enterprise Linux 9 see references

Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

References