FirefoxWeb browser · Mozilla
CVE-2020-12393
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 · uneditedThe 'Copy as cURL' feature of Devtools' network tab did not properly escape the HTTP method of a request, which can be controlled by the website. If a user used the 'Copy as cURL' feature and pasted the command into a terminal, it could have resulted in command injection and arbitrary command execution. *Note: this issue only affects Firefox on Windows operating systems.*. This vulnerability affects Firefox ESR < 68.8, Firefox < 76, and Thunderbird < 68.8.0.
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 confidenceFirefox DevTools 'Copy as cURL' feature fails to properly escape HTTP method values when generating cURL commands. A malicious website can craft an HTTP method containing shell metacharacters that will execute arbitrary commands when the user copies the request and pastes the cURL command into a Windows terminal.
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
FirefoxWeb browser
< 76.0
Firefox EsrWeb browser
< 68.8.0< 68.8.0CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/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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Check Firefox browser versionOpen Firefox, click the menu button (three horizontal lines), select Help, then About Firefox. The version number is displayed on the page.Affected if The displayed version is below 76.0 (for example 75.0, 74.0, etc.)
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Check Firefox ESR versionOpen Firefox ESR, click the menu button, select Help, then About Mozilla Firefox. Look for the version number in the format like 68.7.x.Affected if The displayed version is below 68.8.0 (for example 68.7.0, 68.6.0, etc.)
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Check Thunderbird versionOpen Thunderbird, click the menu button (three horizontal lines), select Help, then About Thunderbird. The version number is displayed.Affected if The displayed version is below 68.8.0 (for example 68.7.0, 68.6.0, etc.)
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Identify if using Windows operating systemThis vulnerability specifically affects Windows terminals when pasting generated cURL commands. Check the operating system via System Properties or 'winver' command.Affected if The system is running Windows and the Firefox/Thunderbird version is in the affected range above
You are affected if you are running Firefox below 76.0, Firefox ESR below 68.8.0, or Thunderbird below 68.8.0 on Windows and have used the DevTools 'Copy as cURL' feature on any website.
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 data68.8.076.0
Update to Firefox ESR 68.8+, Firefox 76+, or Thunderbird 68.8.0+. Until patched, avoid using 'Copy as cURL' on untrusted websites.
Fix this in Firefox
Scoped from the published advisory
- Consultation4.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,040.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-12393 — 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-2020-12393 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
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