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TI-2017-05437 Aliases CVE-2017-7820GHSA-hq9m-2fcc-v974

The "instanceof" operator can bypass the Xray wrapper mechanism.

Priority LOW 26Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · Low · None
Fix status
Fixed

Attack profile from CVSS 3.0 · NVD. Fix status from CNA.

Summary

The "instanceof" operator can bypass the Xray wrapper mechanism. When called on web content from the browser itself or an extension the web content can provide its own result for that operator, possibly tricking the browser or extension into mishandling the element. This vulnerability affects Firefox < 56.

Why it matters now

EPSS 0.01163 67th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed Firefox (Mozilla): 56

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaFirefoxbefore 5656Patch availableCNA
  • Firefox VendorMozilla Affected before 56 Fixed in 56 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*up to 55.0.3VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions up to 55.0.3 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Firefox (Mozilla) Fixed in 56

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    Mozilla Firefox 56

    9 records Highest priority Priority MEDIUM 2 MEDIUM, 7 LOW

    Other records, highest priority first

    • TI-2017-05438 Incorrect permission assignment in Mozilla FirefoxPriority MEDIUM 46
    • TI-2017-05428 Memory corruption in Mozilla FirefoxPriority MEDIUM 46
    • TI-2017-05430 Out-of-bounds read in Mozilla FirefoxPriority LOW 39
    Show all 9 records →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2017-7820
  2. 2026-10-03 Alias added: GHSA-hq9m-2fcc-v974

References

Exploit 1

Advisory 1

  • TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
  • TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
  • TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
  • TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
  • TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
  • TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
See all 3444 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences