CVE-2026-2761Network attack vector

Sandbox escape through undisclosed WebRender flaw

Published Feb 24, 2026 · Updated Feb 24, 2026

Sandbox escape in affected Mozilla Firefox and Thunderbird releases allows remote attackers to breach the WebRender process sandbox. Mozilla identifies Graphics: WebRender as the component but has not disclosed the flawed operation or the access available after escape. Affected builds are Firefox before 148, Firefox ESR before 115.33 or 140.8, and Thunderbird before 140.8 or 148; Thunderbird disables scripting while reading email.

CVSS severity10.0
Critical
EPSS probability0.40%
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 affected Mozilla Firefox and Thunderbird releases allows remote attackers to breach the WebRender process sandbox. Mozilla identifies Graphics: WebRender as the component but has not disclosed the flawed operation or the access available after escape. Affected builds are Firefox before 148, Firefox ESR before 115.33 or 140.8, and Thunderbird before 140.8 or 148; Thunderbird disables scripting while reading email.

The record

CVE
CVE-2026-2761
Published
Feb 24, 2026
Updated
Feb 24, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-693
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 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 <148

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <148
Mozilla · Thunderbirdversion=unspecified <140.8; version=unspecified <148
Mozilla · Firefox ESRversion=unspecified <115.33; version=unspecified <140.8

Published CVSS scores

10.0CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
10.0NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
7.5Red Hat SADPCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/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-693Protection Mechanism Failure

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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