dbcve.org
FirefoxWeb browser · Mozilla

CVE-2020-12415

MEDIUM · 6.5 CVSS v3.1 Published 2020-07-09
Fix available
A fix is available. Upgrade to 78.0 or later.
See remediation →
72/100
Remediation priority · Elevated
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
When "%2F" was present in a manifest URL, Firefox's AppCache behavior may have become confused and allowed a manifest to be served from a subdirectory. This could cause the appcache to be used to service requests for the top level directory. This vulnerability affects Firefox < 78.

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 AppCache implementation incorrectly handled URLs containing '%2F' (URL-encoded forward slash), allowing a manifest from a subdirectory to be used for caching the top-level directory. This path traversal through URL encoding could cause the AppCache to serve content from an unintended location.

MitigationUpgrade Firefox to version 78 or later to obtain the patch. Additionally, consider disabling AppCache on internal applications if not needed, as AppCache is deprecated.

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:< 78.0
LeapOperating system
Affected:= 15.1= 15.2

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
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

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. Determine installed Firefox version
    Open Firefox, navigate to Help > About Firefox, or run 'firefox --version' in terminal
    Affected if Version is below 78.0
  2. Identify if AppCache is in use
    Check web applications for manifest.appcache files or look for <html manifest='...'> tags in served pages; inspect browser traffic for AppCache manifest requests
    Affected if Any web application or page uses AppCache caching mechanism
  3. Verify OpenSUSE Firefox package version (if on OpenSUSE)
    Run 'rpm -qa | grep -i firefox' or check via package manager (zypper)
    Affected if Running Mozilla Firefox package from OpenSUSE Leap 15.1 or 15.2 with version below 78.0

You are affected if your Firefox version is below 78.0 and any application you access uses AppCache for caching.

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 78.0 or later
Fixed in 78.0
Interim mitigation

Upgrade Firefox to version 78 or later to obtain the patch. Additionally, consider disabling AppCache on internal applications if not needed, as AppCache is deprecated.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
3.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

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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-2020-12415 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