CVE-2025-2857Network attack vector

Sandbox escape via unfiltered IPC pseudo-handles

Published Mar 27, 2025 · Updated Jun 9, 2026

Sandbox escape in Mozilla Firefox and Firefox ESR allows remote attackers to escape a compromised child process on Windows. Channel::ChannelImpl::AcceptHandles passes child-supplied pseudo-handle values to DuplicateHandle without rejecting them, so the parent returns a powerful real handle. Exploitation requires control of a sandboxed child process and can grant access to the parent process; only Windows releases before Firefox 136.0.4, ESR 128.8.1, or ESR 115.21.1 are affected.

CVSS severity10.0
Critical
EPSS probability1.90%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Sandbox escape in Mozilla Firefox and Firefox ESR allows remote attackers to escape a compromised child process on Windows. Channel::ChannelImpl::AcceptHandles passes child-supplied pseudo-handle values to DuplicateHandle without rejecting them, so the parent returns a powerful real handle. Exploitation requires control of a sandboxed child process and can grant access to the parent process; only Windows releases before Firefox 136.0.4, ESR 128.8.1, or ESR 115.21.1 are affected.

The record

CVE
CVE-2025-2857
Published
Mar 27, 2025
Updated
Jun 9, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-668, T1068
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 27, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

10.0CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-668Exposure of Resource to Wrong Sphere
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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