Medium severity · published Aug 4, 2026
CVE-2026-70367
Stunnel: ssrf bypass in stunnel socks proxy via ipv4-mapped ipv6 loopback and unspecified addresses allows access to loopback-only services
5.4
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 5% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 9 · Red Hat
All versions, or not specified · source: vendor
ST
stunnel · Mobi-Com Polska Sp. z o.o.
5.25 before 5.80 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-70367
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-70367
access.redhat.com
https://access.redhat.com/security/cve/CVE-2026-70367
bugzilla.redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2462083
More from stunnel
6.5
CVE-2026-70368
Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message