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FirefoxWeb browser · Mozilla

CVE-2017-7837

MEDIUM · 5.3 CVSS v3.0 Published 2018-06-11
Fix available
A fix is available. Upgrade to after 56.0.2 or later.
See remediation →
62/100
Remediation priority · Elevated
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
SVG loaded through "<img>" tags can use "<meta>" tags within the SVG data to set cookies for that page. This vulnerability affects Firefox < 57.

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 allows SVG images loaded via <img> tags to execute <meta> tags within the SVG content, which can set cookies for the parent page. This enables an attacker to manipulate cookies through malicious SVG files, representing a client-side cookie injection vulnerability.

MitigationUpgrade Firefox to version 57 or later. Additionally, implement Content Security Policy (CSP) headers to restrict content sources and consider disabling SVG uploads where not needed.

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:<= 56.0.2

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
Low
Availability
None

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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
    Navigate to about:support or about:firefox in the address bar to view the installed Firefox version number
    Affected if The displayed version is 56.0.2 or lower
  2. Verify SVG image loading behavior
    Load an SVG file embedded via an <img> tag in a test HTML page and inspect whether the SVG content is processed as HTML-like content
    Affected if SVG content is rendered and any <meta> tags within the SVG are processed by the browser
  3. Test for cookie injection via SVG
    Serve a test page with an <img> src pointing to a malicious SVG containing a <meta http-equiv='set-cookie'> tag, then check if cookies are set for the parent domain
    Affected if Cookies are successfully set from the SVG meta tag, indicating the vulnerability is present

A user is affected if they are running Firefox version 56.0.2 or lower and the browser processes meta tags within SVG images loaded via img tags.

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 a release after 56.0.2
Interim mitigation

Upgrade Firefox to version 57 or later. Additionally, implement Content Security Policy (CSP) headers to restrict content sources and consider disabling SVG uploads where not needed.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $750
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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-2017-7837 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