CVE-2026-9966Network attack vectorHinoki check available

Sandbox escape via XML allocation-size truncation

Published May 28, 2026 · Updated May 28, 2026

Integer overflow in Google Chrome's XML component on Windows before 148.0.7778.216 allows remote attackers to attempt a sandbox escape. The libxml2 xmlEscapeText function narrows a computed allocation size to signed int, permitting an undersized allocation and heap-buffer overflow while escaping text. Exploitation requires a compromised renderer and a crafted HTML page; the Chromium fix demonstrates heap corruption, while sandbox escape remains the reported potential impact.

CVSS severity8.3
High
EPSS probability0.21%
Next 30 days · Nov 1, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Integer overflow in Google Chrome's XML component on Windows before 148.0.7778.216 allows remote attackers to attempt a sandbox escape. The libxml2 xmlEscapeText function narrows a computed allocation size to signed int, permitting an undersized allocation and heap-buffer overflow while escaping text. Exploitation requires a compromised renderer and a crafted HTML page; the Chromium fix demonstrates heap corruption, while sandbox escape remains the reported potential impact.

The record

CVE
CVE-2026-9966
Published
May 28, 2026
Updated
May 28, 2026
Vendor
WebM Project
Product
Chrome
Classifications
CWE-472, T1068
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

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

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  1. Affected version<148.0.7778.216

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

WebM Project · Chrome<148.0.7778.216

Published CVSS scores

8.3CISA-ADPCVSS:3.1/AV:N/AC:H/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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-472External Control of Assumed-Immutable Web Parameter
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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