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FirefoxWeb browser · Mozilla

CVE-2020-26952

HIGH · 8.8 CVSS v3.1 Published 2020-12-09
Fix available
A fix is available. Upgrade to 83.0 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

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 · unedited
Incorrect bookkeeping of functions inlined during JIT compilation could have led to memory corruption and a potentially exploitable crash when handling out-of-memory errors. This vulnerability affects Firefox < 83.

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 confidence

Firefox's JIT (Just-In-Time) compiler incorrectly tracked bookkeeping of inlined functions, leading to memory corruption and exploitable crashes specifically triggered when the browser encountered out-of-memory error conditions. This is a flaw in SpiderMonkey's JIT compilation engine's memory management during function inlining.

MitigationUpgrade Firefox to version 83 or later to obtain the patched browser. In enterprise environments, deploy the updated version organization-wide and verify compatibility with internal web applications.

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
Affected:< 83.0

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Firefox version
    Navigate to Menu > Help > About Firefox, or type 'about:support' in the address bar to view the version number under Application Basics
    Affected if Version is lower than 83.0 (e.g., 82.x, 81.x, etc.)
  2. Verify JIT compilation status
    Type 'about:config' in the address bar, search for 'javascript.options.jit' and check if the value is set to true
    Affected if javascript.options.jit is enabled (value is true) - the vulnerability requires JIT to be active
  3. Confirm browser is not an ESR or extended support release
    Check the version string - ESR releases have 'ESR' appended (e.g., 78.x ESR). If using an older ESR, check its base version number
    Affected if Running Firefox ESR with base version below 83 (e.g., Firefox 78 ESR) - these may have separate patching timelines

You are affected if Firefox version is below 83.0 and JIT compilation is enabled, as the memory corruption flaw in SpiderMonkey's JIT inlining occurs specifically during out-of-memory conditions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to 83.0 or later
Fixed in 83.0
Interim mitigation

Upgrade Firefox to version 83 or later to obtain the patched browser. In enterprise environments, deploy the updated version organization-wide and verify compatibility with internal web applications.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.

Scan for this in your stack

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dbcve dependency scanner

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-26952 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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