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FirefoxWeb browser · Mozilla

CVE-2023-4583

HIGH · 7.5 CVSS v3.1 Published 2023-09-11
Fix available
A fix is available. Upgrade to 115.2 / 117.0 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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 checking if the Browsing Context had been discarded in `HttpBaseChannel`, if the load group was not available then it was assumed to have already been discarded which was not always the case for private channels after the private session had ended. This vulnerability affects Firefox < 117, Firefox ESR < 115.2, and Thunderbird < 115.2.

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 confidence

In Mozilla's HttpBaseChannel, when checking if a Browsing Context had been discarded, the code incorrectly assumed the context was already discarded if the load group was unavailable. This logic flaw affects private browsing channels after the private session ends, potentially leading to incorrect security state handling.

MitigationUpdate Firefox to version 117 or later, Firefox ESR to 115.2 or later, and Thunderbird to 115.2 or later to receive the security patch.

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:< 117.0
Firefox EsrWeb browser
Affected:< 115.2
ThunderbirdApplication
Affected:< 115.2

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
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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. Identify the installed Mozilla product
    Check which Mozilla application is installed: Firefox (standard), Firefox ESR, or Thunderbird. On Windows, look in Program Files; on macOS, check /Applications; on Linux, check /usr/lib or /opt.
    Affected if The product is Firefox, Firefox ESR, or Thunderbird.
  2. Check Firefox version
    In Firefox, go to Help > About Firefox, or enter 'about:support' in the address bar. The version number is displayed at the top.
    Affected if Firefox version is below 117.0 (e.g., 116.x, 115.x, or earlier).
  3. Check Firefox ESR version
    In Firefox ESR, go to Help > About Firefox, or enter 'about:support'. ESR versions typically include 'ESR' in the version string (e.g., 115.1esr).
    Affected if Firefox ESR version is below 115.2.
  4. Check Thunderbird version
    In Thunderbird, go to Help > About Thunderbird, or enter 'about:support'. The version number is displayed at the top.
    Affected if Thunderbird version is below 115.2.
  5. Verify if private browsing was used
    This vulnerability specifically affects private browsing channels after a private session ends. Check browser history or log recent private browsing sessions.
    Affected if Private browsing sessions were used and the browser was not updated after the session ended.

The environment is affected if Firefox is below 117.0, Firefox ESR is below 115.2, or Thunderbird is below 115.2, AND private browsing sessions were used in the affected version.

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.

dbcve · scoped
Upgrade available Upgrade to 115.2 / 117.0 or later
Fixed in 115.2117.0
Interim mitigation

Update Firefox to version 117 or later, Firefox ESR to 115.2 or later, and Thunderbird to 115.2 or later to receive the security patch.

Recommended fix High confidence

Firefox 117.0, Firefox ESR 115.2, or Thunderbird 115.2

  1. Check the current version of Firefox, Firefox ESR, or Thunderbird installed (help > about)
  2. Download and install Firefox 117.0 or later, Firefox ESR 115.2 or later, or Thunderbird 115.2 or later from the official Mozilla website (www.mozilla.org)
  3. Restart the application after updating

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.

Scan for this in your stack

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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-2023-4583 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