CVE-2026-86158 Progress Software Fiddler Everywhere - Authentication Bypass

Progress Software Fiddler Everywhere 8.0.2 contains a broken authentication caused by missing authentication in the local .NET backend (Fiddler.WebUi), letting local unauthenticated attackers mint OAuth tokens and read the machine-in-the-middle root certificate through localhost HTTP and SignalR RPC channels.

CVSS base score 7.7 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.09% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Information Disclosure, Broken Authentication
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
29 September 2026
Updated
15 October 2026
Weakness
CWE-306

Vendor fix

Update to the latest version of Progress Software Fiddler Everywhere.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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