CVE-2020-12389Network attack vector

Sandbox escape via weak content-process DACL

Published May 26, 2020 · Updated Aug 4, 2024

Improper access control in Mozilla Firefox before 76 and Firefox ESR before 68.8 allows attackers to escape the Windows content sandbox. SandboxBroker::SetSecurityLevelForContentProcess assigns content processes low integrity without a lockdown default DACL, letting renderers manipulate peer and more-trusted processes. Exploitation requires code execution in a content process and can reach file processes with filesystem access; non-Windows systems are unaffected.

CVSS severity10.0
Critical
EPSS probability1.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Mozilla Firefox before 76 and Firefox ESR before 68.8 allows attackers to escape the Windows content sandbox. SandboxBroker::SetSecurityLevelForContentProcess assigns content processes low integrity without a lockdown default DACL, letting renderers manipulate peer and more-trusted processes. Exploitation requires code execution in a content process and can reach file processes with filesystem access; non-Windows systems are unaffected.

The record

CVE
CVE-2020-12389
Published
May 26, 2020
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-20, T1068
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <76

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <76
Mozilla · Firefox ESRversion=unspecified <68.8

Published CVSS scores

10.0NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
7.5NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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