stunnel up to 5.79 SOCKS Proxy Mode server-side request forgery

Summaryinfo

A vulnerability was found in stunnel up to 5.79. It has been classified as critical. The affected element is an unknown function of the component SOCKS Proxy Mode. This manipulation causes server-side request forgery. This vulnerability is handled as CVE-2026-70367. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability classified as critical was found in stunnel up to 5.79. Affected by this vulnerability is an unknown code block of the component SOCKS Proxy Mode. The manipulation with an unknown input leads to a server-side request forgery vulnerability. The CWE definition for the vulnerability is CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at access.redhat.com. This vulnerability is known as CVE-2026-70367 since 08/04/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/04/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Name

• stunnel

Version

• 5.0
• 5.1
• 5.2
• 5.3
• 5.4
• 5.5
• 5.6
• 5.7
• 5.8
• 5.9
• 5.10
• 5.11
• 5.12
• 5.13
• 5.14
• 5.15
• 5.16
• 5.17
• 5.18
• 5.19
• 5.20
• 5.21
• 5.22
• 5.23
• 5.24
• 5.25
• 5.26
• 5.27
• 5.28
• 5.29
• 5.30
• 5.31
• 5.32
• 5.33
• 5.34
• 5.35
• 5.36
• 5.37
• 5.38
• 5.39
• 5.40
• 5.41
• 5.42
• 5.43
• 5.44
• 5.45
• 5.46
• 5.47
• 5.48
• 5.49
• 5.50
• 5.51
• 5.52
• 5.53
• 5.54
• 5.55
• 5.56
• 5.57
• 5.58
• 5.59
• 5.60
• 5.61
• 5.62
• 5.63
• 5.64
• 5.65
• 5.66
• 5.67
• 5.68
• 5.69
• 5.70
• 5.71
• 5.72
• 5.73
• 5.74
• 5.75
• 5.76
• 5.77
• 5.78
• 5.79

CPE 2.3info

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CPE 2.2info

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