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CVE Record

CVE-2020-13661: Telerik Fiddler through 5.0.20202.18177 allows attackers to execute arbitrary programs via a hostname with...

Telerik Fiddler through 5.0.20202.18177 allows attackers to execute arbitrary programs via a hostname with a trailing space character, followed by --utility-and-browser --utility-cmd-prefix= and the pathname of a locally installed program. The victim must interactively choose the Open On Browser option. Fixed in version 5.0.20204.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2020-13661 affects Telerik Fiddler through 5.0.20202.18177. A crafted hostname could cause arbitrary local program execution, but only if the victim interactively uses Fiddler's Open On Browser option. This is serious for workstations using Fiddler on untrusted traffic, though the sources do not show active exploitation.

Executive priority

Treat as a targeted workstation risk, not an internet-wide emergency. Prioritize remediation for security, QA, and developer endpoints using Fiddler with untrusted traffic.

Technical view

The CVE describes command-line argument injection through a hostname with a trailing space and browser utility arguments. The vulnerable behavior can launch a locally installed program when the user selects Open On Browser. The source bundle names the fix as Fiddler 5.0.20204; no CVSS, CWE, or detailed affected CPE data is provided.

Likely exposure

Exposure is likely limited to endpoints running Telerik Fiddler through 5.0.20202.18177, especially analysts or developers inspecting untrusted hostnames and using Open On Browser.

Exploitation context

The sources support potential arbitrary program execution, not confirmed exploitation. Exploitation requires user interaction and a local program path; KEV status is false in the bundle.

Researcher notes

Evidence is concise: the CVE description provides the vulnerable version range, interaction requirement, and fixed version. The bundle lacks CVSS, CWE, detailed vendor advisory text, and exploitation evidence, so avoid broader claims.

Mitigation direction

  • Upgrade Telerik Fiddler to 5.0.20204 or later.
  • Check Telerik release history for current vendor guidance.
  • Limit Fiddler use on untrusted traffic until upgraded.
  • Warn users not to use Open On Browser on suspicious hostnames.

Validation and detection

  • Inventory installed Fiddler versions across workstations.
  • Confirm vulnerable versions are upgraded or removed.
  • Identify teams using Fiddler for traffic analysis.
  • Review endpoint telemetry for unusual program launches from Fiddler.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2020-13661 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.