dbcve.org
FirefoxWeb browser · Mozilla

CVE-2022-40958

MEDIUM · 6.5 CVSS v3.1 Published 2022-12-22
Fix available
A fix is available. Upgrade to 102.3 / 105.0 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
By injecting a cookie with certain special characters, an attacker on a shared subdomain which is not a secure context could set and thus overwrite cookies from a secure context, leading to session fixation and other attacks. This vulnerability affects Firefox ESR < 102.3, Thunderbird < 102.3, and Firefox < 105.

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

A cookie injection vulnerability in Firefox and Thunderbird allows attackers on shared non-secure subdomains to overwrite cookies intended for secure contexts by injecting specially crafted cookies with certain characters. This enables session fixation attacks where an attacker can hijack a user's session.

MitigationUpdate affected products to Firefox ESR 102.3+, Thunderbird 102.3+, or Firefox 105+. Avoid sharing subdomains between secure and non-secure contexts.

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:< 105.0
Firefox EsrWeb browser
Affected:< 102.3
ThunderbirdApplication
Affected:< 102.3

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. Check Firefox version in browser
    Open Firefox, type 'about:support' in the address bar, and look at the 'Version' field in the 'Application Basics' section
    Affected if The version displayed is below 105.0 (e.g., 104.x, 103.x, etc.) or shows a Firefox ESR version below 102.3
  2. Check Firefox version via command line
    Run 'firefox --version' in a terminal or command prompt
    Affected if The output shows a version below 105.0 for standard Firefox, or below 102.3 for Firefox ESR
  3. Check Thunderbird version in application
    Open Thunderbird, go to Help > About Thunderbird, or type 'about:support' in the address bar
    Affected if The version displayed is below 102.3
  4. Check Thunderbird version via command line
    Run 'thunderbird --version' in a terminal or command prompt
    Affected if The output shows a version below 102.3
  5. Identify shared subdomain usage
    Review your network environment or browser configuration to determine if non-secure (HTTP) and secure (HTTPS) services share the same parent domain (e.g., apps.example.com and example.com)
    Affected if You operate in an environment where both HTTP and HTTPS services share subdomains under the same parent domain, AND you are running an affected version listed above

You are affected if you are running any version of Firefox below 105.0, Firefox ESR below 102.3, or Thunderbird below 102.3, especially in environments with shared subdomains between HTTP and HTTPS contexts.

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 102.3 / 105.0 or later
Fixed in 102.3105.0
Interim mitigation

Update affected products to Firefox ESR 102.3+, Thunderbird 102.3+, or Firefox 105+. Avoid sharing subdomains between secure and non-secure contexts.

Recommended fix High confidence

Firefox 105.0, Firefox ESR 102.3, or Thunderbird 102.3

  1. Back up any important data such as bookmarks, saved passwords, and email data
  2. Open Firefox or Thunderbird
  3. Navigate to the application menu and select 'Help' > 'About Firefox' or 'About Thunderbird'
  4. The application will check for updates and automatically download version 105.0 (Firefox) or 102.3 (Firefox ESR/Thunderbird)
  5. Restart the application to complete the installation
  6. Verify the update by returning to Help > About and confirming the version number

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

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.

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-2022-40958 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