High severity · published Sep 29, 2026
CVE-2026-86158
Missing Authentication in the local .NET backend of Progress Telerik Fiddler Everywhere
7.7
CVSS
0.1%
EPSS
No
On KEV
Description
Missing authentication in the local .NET backend (Fiddler.WebUi) of Progress Software Fiddler Everywhere 8.0.2 allows a local unauthenticated attacker to mint OAuth tokens and read the machine-in-the-middle root certificate through an unauthenticated localhost HTTP and SignalR RPC channel.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 0% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PT
Progress® Telerik® Fiddler® Everywhere · Progress Software
1.0.0 before 8.2.0 · source: vendor
Affected product
PT
Progress® Telerik® Fiddler® Everywhere
Progress Software
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-86158
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-86158
vendor-advisory
https://www.telerik.com/fiddler/fiddler-everywhere/documentation/knowledge-base/kb-security-missing-authentication-for-critical-function-cve-2026-86158
More from Progress® Telerik® Fiddler® Everywhere
5.6
CVE-2026-86157
Exposure of Privileged IPC Functionality in Progress Telerik Fiddler Everywhere