CVE-2026-7321Network attack vector

Sandbox escape via WebRTC networking boundary error

Published Apr 28, 2026 · Updated Apr 28, 2026

Incorrect boundary conditions in Firefox and Thunderbird before 150, including ESR before 140.10.1, allow remote attackers to escape the sandbox. Mozilla has not disclosed which operation in WebRTC networking applies the incorrect boundary check to untrusted input. Exploitation requires user interaction and can cross the content-process sandbox boundary, but no public code-execution mechanism is documented.

CVSS severity9.6
Critical
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect boundary conditions in Firefox and Thunderbird before 150, including ESR before 140.10.1, allow remote attackers to escape the sandbox. Mozilla has not disclosed which operation in WebRTC networking applies the incorrect boundary check to untrusted input. Exploitation requires user interaction and can cross the content-process sandbox boundary, but no public code-execution mechanism is documented.

The record

CVE
CVE-2026-7321
Published
Apr 28, 2026
Updated
Apr 28, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-120, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 28, 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

9.6CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/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.

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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-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1203Exploitation for Client Execution

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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