CVE-2026-5733Network attack vector

Memory corruption via WebGPU out-of-bounds write

Published Apr 7, 2026 · Updated Apr 7, 2026

Out-of-bounds write in Mozilla Firefox and Thunderbird before 149.0.2 allows remote attackers to corrupt memory via crafted WebGPU content. The restricted Mozilla bug leaves the precise WebGPU boundary check and unsafe write operation undisclosed. Exploitation requires user interaction with network-delivered content; Thunderbird disables scripting while reading mail, limiting ordinary email exposure, but browser-like contexts remain affected.

CVSS severity8.8
High
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Mozilla Firefox and Thunderbird before 149.0.2 allows remote attackers to corrupt memory via crafted WebGPU content. The restricted Mozilla bug leaves the precise WebGPU boundary check and unsafe write operation undisclosed. Exploitation requires user interaction with network-delivered content; Thunderbird disables scripting while reading mail, limiting ordinary email exposure, but browser-like contexts remain affected.

The record

CVE
CVE-2026-5733
Published
Apr 7, 2026
Updated
Apr 7, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-787, CWE-119, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 7, 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 <149.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <149.0.2
Mozilla · Thunderbirdversion=unspecified <149.0.2

Published CVSS scores

8.8Red Hat SADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.8CISA-ADPCVSS:3.1/AV:N/AC:L/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 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-787Out-of-bounds Write
CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
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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