dbcve.org
FirefoxWeb browser · Mozilla

CVE-2023-5173

HIGH · 7.5 CVSS v3.1 Published 2023-09-27
Fix available
A fix is available. Upgrade to 118 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
In a non-standard configuration of Firefox, an integer overflow could have occurred based on network traffic (possibly under influence of a local unprivileged webpage), leading to an out-of-bounds write to privileged process memory. *This bug only affects Firefox if a non-standard preference allowing non-HTTPS Alternate Services (`network.http.altsvc.oe`) is enabled.* This vulnerability affects Firefox < 118.

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

Integer overflow in Firefox's Alternate Services handling when the non-standard network.http.altsvc.oe preference is enabled, allowing out-of-bounds memory write to privileged process memory via crafted network traffic possibly influenced by a local unprivileged webpage.

MitigationDisable the network.http.altsvc.oe preference if enabled, and upgrade Firefox to version 118 or later.

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:< 118

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. Check Firefox version
    Open Firefox, navigate to about:support, or run 'firefox --version' from command line, or check the application file version
    Affected if Version is below 118 (e.g., 117.x, 116.x, etc.)
  2. Check if preference network.http.altsvc.oe exists and is enabled
    Navigate to about:config in Firefox address bar, search for 'network.http.altsvc.oe', and observe the value (boolean true means enabled)
    Affected if The preference value is set to true (enabled)
  3. Verify affected condition
    Combine version and preference checks: you are affected if running Firefox version below 118 AND the network.http.altsvc.oe preference is enabled
    Affected if Both conditions are true: Firefox < 118 AND network.http.altsvc.oe = true

You are affected only if running Firefox versions below 118 with the non-standard network.http.altsvc.oe preference enabled.

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 118 or later
Fixed in 118
Interim mitigation

Disable the network.http.altsvc.oe preference if enabled, and upgrade Firefox to version 118 or later.

Recommended fix High confidence

Firefox 118

  1. 1. Back up any important bookmarks, passwords, and browser data from the current Firefox installation
  2. 2. Check the current Firefox version by navigating to Menu > Help > About Firefox
  3. 3. If Firefox version is below 118, initiate an update: Menu > Help > About Firefox > Check for Updates
  4. 4. If automatic update is unavailable, download Firefox 118 or later from the official Mozilla website (www.mozilla.org)
  5. 5. Install the updated Firefox version, ensuring all previous browser sessions are closed
  6. 6. Alternatively, for enterprise deployments, use the Firefox ESR channel or deployment tools (e.g., Group Policy, MDM) to push the upgrade to version 118 or later
  7. 7. After upgrade, optionally verify the fix by checking Menu > Help > About Firefox shows version 118 or higher

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,090
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,744.

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-2023-5173 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