Progress Telerik Fiddler Everywhere up to 8.1.x Fiddler.WebUi missing authentication

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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6.4$0-$5k1.29

Summaryinfo

A vulnerability has been found in Progress Telerik Fiddler Everywhere up to 8.1.x and classified as problematic. This issue affects some unknown processing of the component Fiddler.WebUi. The manipulation leads to missing authentication. This vulnerability is traded as CVE-2026-86158. An attack has to be approached locally. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Progress Telerik Fiddler Everywhere up to 8.1.x. This issue affects an unknown part of the component Fiddler.WebUi. The manipulation with an unknown input leads to a missing authentication vulnerability. Using CWE to declare the problem leads to CWE-306. The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at telerik.com. The identification of this vulnerability is CVE-2026-86158 since 09/05/2026. The exploitation is known to be easy. Attacking locally is a requirement. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 8.2.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-88649). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.5
VulDB Meta Temp Score: 6.4

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.7
CNA Vector (ProgressSoftware): 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Missing authentication
CWE: CWE-306 / CWE-287
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Telerik Fiddler Everywhere 8.2.0

Timelineinfo

09/05/2026 CVE reserved
09/29/2026 +24 days Advisory disclosed
09/29/2026 +0 days VulDB entry created
09/29/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: telerik.com
Status: Confirmed

CVE: CVE-2026-86158 (🔒)
GCVE (CVE): GCVE-0-2026-86158
GCVE (VulDB): GCVE-100-411239
EUVD: 🔒

Entryinfo

Created: 09/29/2026 09:00
Updated: 09/29/2026 10:30
Changes: 09/29/2026 09:00 (63), 09/29/2026 10:30 (1)
Complete: 🔍
Cache ID: 216::103

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

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