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Fencer Vulns
medium 5.4

CVE-2026-70367 json

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

published 2026-08-04 3 mo ago modified 2026-11-05 3 d ago also EUVD-2026-52687

cvss
5.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 13%
public exploits
0
none known

Summary

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.

Patch / fix

  • Mobi-Com Polska Sp. z o.o. stunnel 5.80
  • stunnel Debian 14 3:5.80-1

debian advisories DEBIAN-CVE-2026-70367

  • stunnel SLES for SAP applications 16.0, SLES 16.0 5.74-160000.3.1
  • stunnel SLE Module for Server Applications 15 SP7 5.70-150600.3.6.1

suse advisories SUSE-SU-2026:24232-1SUSE-SU-2026:4617-1

  • stunnel openSUSE Leap 16.0 5.74-160000.3.1
  • stunnel openSUSE Tumbleweed 5.80-1.1

opensuse advisories openSUSE-SU-2026:22088-1openSUSE-SU-2026:11500-1

  • stunnel Alpine 3.24 5.82-r0

alpine advisories ALPINE-CVE-2026-70367

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-70367 updated cvss 5.4

stunnel: SSRF bypass in stunnel SOCKS proxy via IPv4-mapped IPv6 loopback and unspecified addresses allows access to loopback-only services

  • Red Hat Enterprise Linux 8 stunnel Red Hat Enterprise Linux 9 stunnel Red Hat Enterprise Linux 10 stunnel
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 stunnel Red Hat Enterprise Linux 7 stunnel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.22% chance of exploitation in the next 30 days, higher than 13% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugzilla.redhat.com https://bugzilla.redhat.com/show_bug.cgi?id=2462083 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Affected products

  • Mobi-Com Polska Sp. z o.o. stunnel
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9

Classification

Weakness
  • CWE-918 Server-Side Request Forgery

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.