FirefoxWeb browser · Mozilla
CVE-2020-35113
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 · uneditedMozilla developers reported memory safety bugs present in Firefox 83 and Firefox ESR 78.5. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 84, Thunderbird < 78.6, and Firefox ESR < 78.6.
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 · moderate confidenceMemory safety bugs in Firefox 83 and Firefox ESR 78.5 caused memory corruption that could potentially be exploited for arbitrary code execution. This is a class of vulnerability affecting Mozilla products where insufficient memory management allows attackers to corrupt memory and potentially execute arbitrary code.
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
< 84.0
Firefox EsrWeb browser
< 78.6.0< 78.6.0CVSS 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 installed Mozilla productCheck if Firefox, Firefox ESR, or Thunderbird is installed. On Windows, look in Program Files or use 'Get-ItemProperty' in PowerShell for registry keys under HKLM:\SOFTWARE\Mozilla\Mozilla Firefox. On Linux, use 'dpkg -l' or 'rpm -qa' to list installed packages. On macOS, check /Applications folder or use 'ls /Applications'.Affected if Any of these three products is installed, proceed to version check.
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Determine Firefox versionIf Firefox is installed, type 'about:firefox' in the address bar or run 'firefox --version' from command line to obtain the exact version number.Affected if Version is less than 84.0, the environment is vulnerable.
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Determine Firefox ESR versionIf Firefox ESR is installed, type 'about:firefox' in the address bar or run 'firefox --version' from command line. ESR versions typically include 'ESR' in the version string, for example '78.5.0esr'.Affected if Version is less than 78.6.0 (or 78.6.0esr), the environment is vulnerable.
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Determine Thunderbird versionIf Thunderbird is installed, type 'about:thunderbird' in the address bar or run 'thunderbird --version' from command line to obtain the exact version number.Affected if Version is less than 78.6.0, the environment is vulnerable.
The environment is affected if any installed Mozilla product (Firefox < 84.0, Firefox ESR < 78.6.0, or Thunderbird < 78.6.0) matches the vulnerable version ranges.
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 data78.6.084.0
Upgrade to Firefox 84 or later, Thunderbird 78.6 or later, or Firefox ESR 78.6 or later to apply vendor patches addressing these memory safety issues.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 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 $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-35113 — 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-2020-35113 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
- No spam, self-promotion, credentials, or personal data