FirefoxWeb browser · Mozilla
CVE-2018-5122
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 · uneditedA potential integer overflow in the "DoCrypt" function of WebCrypto was identified. If a means was found of exploiting it, it could result in an out-of-bounds write. This vulnerability affects Firefox < 58.
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 confidenceAn integer overflow vulnerability exists in the DoCrypt function of Firefox's WebCrypto implementation. When exploited, the overflow can cause an out-of-bounds memory write, potentially allowing attackers to execute arbitrary code. This is a critical memory safety flaw in cryptographic operations.
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
<= 57.0.4
Ubuntu LinuxOperating system
= 14.04= 16.04= 17.10CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/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 checksWork through these to decide whether this CVE applies to you.
-
Check Firefox version on Windows or macOSOpen Firefox, click Help > About Firefox, or run 'firefox --version' from command lineAffected if Version displays 57.0.4 or lower (e.g., 57.0, 57.0.3, 57.0.4)
-
Check Firefox package version on Ubuntu LinuxRun 'dpkg -l | grep firefox' or 'apt-cache policy firefox' in terminalAffected if Installed firefox version is 57.0.4 or lower according to the package listing
-
Verify WebCrypto API is enabled in FirefoxType 'about:config' in the Firefox address bar, search for 'crypto.webapi.enabled', and confirm the value is set to trueAffected if crypto.webapi.enabled is set to true (default) - the vulnerability only applies when WebCrypto is enabled
-
Confirm the specific Ubuntu releaseRun 'lsb_release -r' or check '/etc/lsb-release'Affected if System runs Ubuntu 14.04, 16.04, or 17.10 AND has Firefox version 57.0.4 or lower installed
A user is affected if Firefox version is 57.0.4 or lower and the WebCrypto API is enabled in the browser settings.
Generated from the published advisory. Verify against your own configuration.
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 · scopedUpdate Firefox to version 58 or later. Organizations should leverage patch management systems to ensure all endpoints have the corrected browser version deployed.
Firefox 58.0 or later (or apply Ubuntu security updates USN-3531-1 and USN-3531-2)
- Upgrade Firefox to version 58.0 or later to remediate the integer overflow vulnerability in the WebCrypto 'DoCrypt' function
- On Ubuntu systems, apply available security updates via: sudo apt-get update && sudo apt-get upgrade firefox or sudo apt-get dist-upgrade
- Verify the Firefox version by navigating to about:firefox or checking Help > About Firefox
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
- Testing1.0 h
- Review / QA1.0 h
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
Free · runs locallyCheck whether your project pulls in CVE-2018-5122 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-5122 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- 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