FirefoxWeb browser · Mozilla
CVE-2016-5276
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 · uneditedUse-after-free vulnerability in the mozilla::a11y::DocAccessible::ProcessInvalidationList function in Mozilla Firefox before 49.0, Firefox ESR 45.x before 45.4, and Thunderbird < 45.4 allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via an aria-owns attribute.
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 confidenceUse-after-free vulnerability in Mozilla's accessibility subsystem (DocAccessible::ProcessInvalidationList) where handling of the aria-owns attribute causes freed memory to be accessed, leading to heap corruption that can be exploited for arbitrary code execution.
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
<= 48.0.2= 45.1.0= 45.1.1= 45.2.0= 45.3.0CVSS 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.
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Determine installed Firefox versionOpen Firefox, go to Help > About Firefox, or run 'firefox --version' from command line. On Windows, check the executable properties. On Linux, check the package manager or run 'rpm -q firefox' or 'dpkg -l firefox'.Affected if Version is 45.1.0, 45.1.1, 45.2.0, 45.3.0, or any version through 48.0.2
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Confirm accessibility subsystem is enabledIn Firefox, go to about:config and verify the accessibility.activenessFlag preference is not set to 0, or check that no enterprise policy or addon is disabling accessibility. Default is enabled.Affected if Accessibility is enabled (default state) - the vulnerability exists in the accessibility subsystem code path
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Identify content using aria-owns attributeInspect web pages or applications loaded in the browser for usage of the aria-owns attribute on elements. Use browser developer tools or search page source for 'aria-owns'.Affected if Content containing aria-owns attribute is loaded while using a vulnerable Firefox version with accessibility enabled
User is affected if running Firefox version 45.1.0-45.3.0 or any version through 48.0.2, with the accessibility subsystem enabled, while processing content that utilizes the aria-owns attribute.
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 to Firefox 49.0+, Firefox ESR 45.4+, or Thunderbird 45.4+ to apply the patched version containing the fix for this accessibility subsystem memory corruption.
Firefox 49.0+ or Firefox ESR 45.4+
- Upgrade to Firefox 49.0 or later
- If using Firefox ESR, upgrade to Firefox ESR 45.4 or later
- If using Thunderbird, upgrade to Thunderbird 45.4 or later
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 h
- Testing2.0 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 $1,664.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-5276 — 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-2016-5276 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
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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
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