CVE-2026-4690Network attack vector

Sandbox escape via XPCOM integer overflow

Published Mar 24, 2026 · Updated Mar 24, 2026

Integer overflow in Mozilla Firefox, Firefox ESR, and Thunderbird allows attackers to escape the content sandbox via XPCOM boundary errors. The XPCOM component applies incorrect boundary conditions that permit an integer overflow, but Mozilla has not disclosed the affected function or input operation. Exploitation requires attacker-controlled content to reach a sandboxed process; success breaks isolation between that content and the privileged host process.

CVSS severity8.6
High
EPSS probability0.77%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in Mozilla Firefox, Firefox ESR, and Thunderbird allows attackers to escape the content sandbox via XPCOM boundary errors. The XPCOM component applies incorrect boundary conditions that permit an integer overflow, but Mozilla has not disclosed the affected function or input operation. Exploitation requires attacker-controlled content to reach a sandboxed process; success breaks isolation between that content and the privileged host process.

The record

CVE
CVE-2026-4690
Published
Mar 24, 2026
Updated
Mar 24, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-190, CWE-120, T1068
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 24, 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?

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

  1. Affected versionversion=unspecified <149

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <149
Mozilla · Thunderbirdversion=unspecified <140.9; version=unspecified <149
Mozilla · Firefox ESRversion=unspecified <115.34; version=unspecified <140.9

Published CVSS scores

9.6CISA ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
8.6NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/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 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-190Integer Overflow or Wraparound
CWE-120Classic Buffer Overflow
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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