Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Network-reachable SOCKS proxy requires low-privilege client access; limited read/write impact against loopback services; no availability or scope change.
Primary rating from Vendor (redhat).
CVSS VectorVendor: redhat
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
SSRF bypass in stunnel 5.79 and earlier allows authenticated SOCKS proxy clients to circumvent intended localhost access restrictions by supplying IPv4-mapped IPv6 addresses (e.g., ::ffff:127.0.0.1) or unspecified addresses (0.0.0.0, ::) in proxy requests. Exploitation reaches loopback-bound services on the stunnel host - services deliberately isolated from external network access - potentially exposing internal APIs, administrative interfaces, or other localhost-only endpoints. No public exploit code has been identified and this vulnerability is not listed in the CISA KEV catalog at time of analysis.
Technical ContextAI
stunnel is a widely-deployed SSL/TLS tunneling daemon that can operate as a SOCKS proxy, forwarding client connections to upstream targets while enforcing access policies. The flaw resides in stunnel's SOCKS-mode address validation logic, which fails to normalize or reject alternative representations of the loopback address before applying its localhost restriction. CWE-918 (Server-Side Request Forgery) covers this root cause class: the server-side proxy component can be manipulated to initiate connections to unintended internal targets. The dual-stack address ambiguity - where ::ffff:127.0.0.1 is a valid IPv6 representation of 127.0.0.1 but may bypass IPv4-only allow/deny checks, and where 0.0.0.0 or :: resolve to the local stack - is a known pitfall in network address validation. Red Hat reports the issue across stunnel as packaged in RHEL 6 through 10 (CPE: cpe:2.3:a:red_hat:red_hat_enterprise_linux_*), confirming broad distribution-level exposure across the RHEL ecosystem.
RemediationAI
No explicit patched version number is identified in the available references. Consult the Red Hat Security Advisory at https://access.redhat.com/security/cve/CVE-2026-70367 and Red Hat Bugzilla ticket 2462083 for updated RHEL packages as they become available; RHEL users should apply the relevant errata once released. For upstream stunnel, monitor the official stunnel.org release channel for a version superseding 5.79 that addresses SOCKS address normalization. As a compensating control, disable SOCKS proxy mode in stunnel configurations if it is not operationally required - this fully eliminates the attack surface with no functional impact for non-SOCKS deployments. Where SOCKS mode is necessary, enforce network-layer ACLs to restrict which clients can reach the stunnel SOCKS port, reducing the pool of potential abusers. Additionally, audit and harden loopback-bound services on the stunnel host to require authentication independently, ensuring that even if loopback restrictions are bypassed, the internal services are not trivially accessible.
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View allVendor StatusVendor
SUSE
Severity: Moderate| Product | Status |
|---|---|
| SUSE Linux Enterprise High Performance Computing 12 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | Affected |
| SUSE Linux Enterprise Module for Server Applications 15 SP7 | Affected |
| SUSE Linux Enterprise Server 15 SP7 | Affected |
| SUSE Linux Enterprise Server 16.0 | Affected |
| SUSE Linux Enterprise Server 16.1 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.0 | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | Affected |
| openSUSE Leap 16.0 | Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP5 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Module for Server Applications 15 SP4 | Affected |
| SUSE Linux Enterprise Module for Server Applications 15 SP5 | Affected |
| SUSE Linux Enterprise Module for Server Applications 15 SP6 | Affected |
| SUSE Linux Enterprise Server 12 SP5 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS Extended Security | Not-Affected |
| SUSE Linux Enterprise Server 15 SP4 | Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP5 | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP6 | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Affected |
| SUSE Linux Enterprise Server LTSS Extended Security 12 SP5 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | Affected |
| SUSE Manager Proxy 4.3 | Affected |
| SUSE Manager Proxy LTS 4.3 | Affected |
| SUSE Manager Retail Branch Server 4.3 | Affected |
| SUSE Manager Retail Branch Server LTS 4.3 | Affected |
| SUSE Manager Server 4.3 | Affected |
| SUSE Manager Server LTS 4.3 | Affected |
| SUSE CaaS Platform 4.0 | Affected |
| SUSE Enterprise Storage 6 | Affected |
| SUSE Enterprise Storage 7 | Affected |
| SUSE Enterprise Storage 7.1 | Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP1 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP2 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP3 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP4 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP6 | Affected |
| SUSE Linux Enterprise High Performance Computing 15-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15-LTSS | Affected |
| SUSE Linux Enterprise Module for Server Applications 15 | Affected |
| SUSE Linux Enterprise Module for Server Applications 15 SP1 | Affected |
| SUSE Linux Enterprise Module for Server Applications 15 SP2 | Affected |
| SUSE Linux Enterprise Module for Server Applications 15 SP3 | Affected |
| SUSE Linux Enterprise Point of Sale 12 SP2-CLIENT | Not-Affected |
| SUSE Linux Enterprise Real Time 15 SP2 | Affected |
| SUSE Linux Enterprise Real Time 15 SP3 | Affected |
| SUSE Linux Enterprise Real Time 15 SP4 | Affected |
| SUSE Linux Enterprise Server 12 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP1 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP1-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP2 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP2-BCL | Not-Affected |
| SUSE Linux Enterprise Server 12 SP2-ESPOS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP2-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP3 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP3-BCL | Not-Affected |
| SUSE Linux Enterprise Server 12 SP3-ESPOS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP3-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP4 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP4-ESPOS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP4-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 15 | Affected |
| SUSE Linux Enterprise Server 15 SP1 | Affected |
| SUSE Linux Enterprise Server 15 SP1-BCL | Affected |
| SUSE Linux Enterprise Server 15 SP1-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP2 | Affected |
| SUSE Linux Enterprise Server 15 SP2-BCL | Affected |
| SUSE Linux Enterprise Server 15 SP2-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP3 | Affected |
| SUSE Linux Enterprise Server 15 SP3-BCL | Affected |
| SUSE Linux Enterprise Server 15 SP3-LTSS | Affected |
| SUSE Linux Enterprise Server 15-LTSS | Affected |
| SUSE Linux Enterprise Server for Raspberry Pi 12 SP2 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP1 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP2 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP3 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP4 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP1 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP2 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP3 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | Affected |
| SUSE Manager Proxy 4.0 | Affected |
| SUSE Manager Proxy 4.1 | Affected |
| SUSE Manager Proxy 4.2 | Affected |
| SUSE Manager Retail Branch Server 4.0 | Affected |
| SUSE Manager Retail Branch Server 4.1 | Affected |
| SUSE Manager Retail Branch Server 4.2 | Affected |
| SUSE Manager Server 4.0 | Affected |
| SUSE Manager Server 4.1 | Affected |
| SUSE Manager Server 4.2 | Affected |
| SUSE OpenStack Cloud 7 | Not-Affected |
| SUSE OpenStack Cloud 8 | Not-Affected |
| SUSE OpenStack Cloud 9 | Not-Affected |
| SUSE OpenStack Cloud Crowbar 8 | Not-Affected |
| SUSE OpenStack Cloud Crowbar 9 | Not-Affected |
| openSUSE Leap 15.3 | Affected |
| openSUSE Leap 15.4 | Affected |
| openSUSE Leap 15.5 | Affected |
| openSUSE Leap 15.6 | Affected |
| suse/stunnel | Affected |
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-52687
GHSA-2x69-8qrg-27gr