FirefoxWeb browser · Mozilla
CVE-2020-6822
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 · uneditedOn 32-bit builds, an out of bounds write could have occurred when processing an image larger than 4 GB in <code>GMPDecodeData</code>. It is possible that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Thunderbird < 68.7.0, Firefox ESR < 68.7, and Firefox < 75.
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 confidenceA memory corruption vulnerability in the GMPDecodeData function allows an out-of-bounds write on 32-bit builds when processing images larger than 4 GB, potentially enabling arbitrary code execution.
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
< 75.0
Firefox EsrWeb browser
< 68.7.0< 68.7.0CVSS 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
- 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 the installed Mozilla productOpen the application and navigate to Help > About, or check the program files folder for firefox.exe or thunderbird.exeAffected if The product is Mozilla Firefox, Firefox ESR, or Mozilla Thunderbird
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Check the installed versionIn Help > About, note the full version number displayed (e.g., 75.0 for Firefox, 68.6.0 for ESR/Thunderbird)Affected if Version is less than 75.0 for Firefox, or less than 68.7.0 for Firefox ESR or Thunderbird
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Determine if the installation is 32-bitCheck the program files folder: 32-bit programs typically reside in C:\Program Files (x86)\Mozilla Firefox, while 64-bit are in C:\Program Files\Mozilla Firefox. Alternatively, right-click the .exe file, go to Properties, and check the Compatibility tab or use Task Manager to view the process architectureAffected if The installation is a 32-bit (x86) build of Firefox, Firefox ESR, or Thunderbird
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Verify large image processing capabilityThe vulnerability triggers when processing images larger than 4 GB through the GMPDecodeData function. Check if the browser or mail client has functionality to decode or display large image filesAffected if The system can process images exceeding 4 GB in size through the affected application
The environment is affected if a 32-bit version of Firefox (<75.0), Firefox ESR (<68.7.0), or Thunderbird (<68.7.0) is installed and the system can process images larger than 4 GB.
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 data68.7.075.0
Upgrade affected installations (Thunderbird to >=68.7.0, Firefox ESR to >=68.7, Firefox to >=75). Specifically prioritize 32-bit systems as the attack surface is limited to that architecture.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation1.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,456.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-6822 — 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-2020-6822 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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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