CVE-2026-11326Public exploitNetwork attack vector

Browser control and history disclosure via overbroad allowlist

Published Jun 5, 2026 · Updated Jun 5, 2026

Improper access control in OpenAI ChatGPT Atlas before 1.2025.288.15 allows remote attackers to read browser history and control tabs. An overbroad origin allowlist exposes Chromium Mojo bindings and LocalToolHandler methods to every *.openai.com page instead of limiting them to trusted browser UI. Exploitation requires a user to visit attacker-controlled content that triggers a forum.openai.com postMessage XSS; the resulting script can enumerate navigation URLs and open or close tabs.

CVSS severity6.0
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in OpenAI ChatGPT Atlas before 1.2025.288.15 allows remote attackers to read browser history and control tabs. An overbroad origin allowlist exposes Chromium Mojo bindings and LocalToolHandler methods to every *.openai.com page instead of limiting them to trusted browser UI. Exploitation requires a user to visit attacker-controlled content that triggers a forum.openai.com postMessage XSS; the resulting script can enumerate navigation URLs and open or close tabs.

The record

CVE
CVE-2026-11326
Published
Jun 5, 2026
Updated
Jun 5, 2026
Vendor
OpenAI
Product
ChatGPT Atlas
Classifications
CWE-284, T1217
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 5, 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=0 <1.2025.288.15

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenAI · ChatGPT Atlasversion=0 <1.2025.288.15

Published CVSS scores

6.0OpenAICVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

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-284Improper Access Control
T1217Browser Information Discovery

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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