CVE-2016-9904: Mozilla Firefox vulnerability

CVE-2016-9904: An attacker could use a JavaScript Map/Set timing attack to determine whether an atom is used by another co...

An attacker could use a JavaScript Map/Set timing attack to determine whether an atom is used by another compartment/zone in specific contexts. This could be used to leak information, such as usernames embedded in JavaScript code, across websites. This vulnerability affects Firefox < 50.1, Firefox ESR < 45.6, and Thunderbird < 45.6.

UnknownCVSS not scoredNot KEV-listedUpdatedAug 6, 2024, 03:07 UTC (UTC+00:00)

Security readout for executives and security teams

CVE-2016-9904 is a browser-side information leak. Malicious JavaScript could use timing differences in Map/Set behavior to infer whether certain internal strings were already used elsewhere, potentially exposing data such as usernames embedded in JavaScript across sites. Exposure is mainly limited to organizations still running the old affected Mozilla versions, including legacy desktops, VDI images, kiosks, or distribution-packaged Firefox and Thunderbird builds from that era. Treat this as a legacy exposure cleanup item. It is not listed as known exploited, but obsolete browsers and mail clients create broader business risk beyond this single issue. Mitigation focus: Upgrade Firefox to 50.1 or later.; Upgrade Firefox ESR to 45.6 or later.; Upgrade Thunderbird to 45.6 or later..

Prepared: Jun 7, 2026, 06:44 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record

Severity: Unknown
CVSS: Not scored
Known Exploited: No
Published: Jun 11, 2018, 21:00 UTC (UTC+00:00)

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors

0Timeline events

0ADP providers

7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

CVE List V5 sourceCVE List V5
https://www.mozilla.org/security/advisories/mfsa2016-94/CVE reference · x_refsource_CONFIRM
https://bugzilla.mozilla.org/show_bug.cgi?id=1317936CVE reference · x_refsource_CONFIRM
https://www.mozilla.org/security/advisories/mfsa2016-95/CVE reference · x_refsource_CONFIRM
GLSA-201701-15CVE reference · vendor-advisory, x_refsource_GENTOO
DSA-3757CVE reference · vendor-advisory, x_refsource_DEBIAN
https://www.mozilla.org/security/advisories/mfsa2016-96/CVE reference · x_refsource_CONFIRM

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus

MozillaFirefoxunspecifiedListed

MozillaFirefox ESRunspecifiedListed

MozillaThunderbirdunspecifiedListed

Weakness

CWE details

No CWE listed

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