CVE-2026-8390Public exploitNetwork attack vector

Renderer code execution via stale WebAssembly pointer

Published May 12, 2026 · Updated May 12, 2026

Use-after-free in Firefox before 150.0.3 allows remote attackers to gain renderer code execution via crafted WebAssembly content. Ion array.copy lowering retains a source data pointer across WasmArrayRefsMove after dropping the source array, allowing minor garbage collection to free the referenced out-of-line block before reuse. A public demonstration requires Firefox to load an attacker-hosted page and disables the content sandbox before converting the stale pointer into arbitrary read, arbitrary write, and shellcode execution.

CVSS severity7.3
High
EPSS probability0.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Firefox before 150.0.3 allows remote attackers to gain renderer code execution via crafted WebAssembly content. Ion array.copy lowering retains a source data pointer across WasmArrayRefsMove after dropping the source array, allowing minor garbage collection to free the referenced out-of-line block before reuse. A public demonstration requires Firefox to load an attacker-hosted page and disables the content sandbox before converting the stale pointer into arbitrary read, arbitrary write, and shellcode execution.

The record

CVE
CVE-2026-8390
Published
May 12, 2026
Updated
May 12, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, CWE-825, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 12, 2026CVE publishedPublication date reported by the CVE source.
  2. May 12, 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

7.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
7.5redhat-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 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 exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
CWE-825Expired Pointer Dereference
T1203Exploitation for Client Execution

Public exploit references

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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