CVE-2020-13661
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedTelerik 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceTelerik Fiddler through version 5.0.20202.18177 contains a command injection vulnerability in its browser launching feature. Attackers can execute arbitrary programs by crafting a hostname with a trailing space character and appending '--utility-and-browser --utility-cmd-prefix=' followed by the pathname of a locally installed program. Exploitation requires the victim to interactively select the 'Open On Browser' option.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 5.0.20202.18177CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Telerik Fiddler versionLaunch Telerik Fiddler and navigate to Help > About, or check the application's title bar which typically displays the version numberAffected if The displayed version is 5.0.20202.18177 or lower (any version up to and including 5.0.20202.18177)
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Verify browser launch feature existsLocate the 'Open On Browser' option in the Fiddler interface - typically found in the File menu or as a toolbar button for launching URLs in a browserAffected if The 'Open On Browser' feature is present and accessible in the installed version
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Confirm interactive usage patternDetermine whether the 'Open On Browser' feature requires user interaction to trigger - the vulnerability exploits the act of selecting this option with a crafted URLAffected if The feature requires interactive selection by the user (not automated)
You are affected if your installed Telerik Fiddler version is 5.0.20202.18177 or lower AND you have access to and use the 'Open On Browser' feature interactively.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade to Telerik Fiddler version 5.0.20204 or later. Until upgrade is completed, avoid using the 'Open On Browser' feature with untrusted URLs.
- Consultation2.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-13661 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-13661 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data